Leo was born May 6, 1924 in San Francisco, California, the son of Christopher Wyatt, and grew up in Burlingame, California. Little is known about his childhood or life before becoming a Whitelighter, save the fact he was studying to be a doctor and married to a woman named Lillian although, he had no children.
Leo served as a medic for the United States Army in World War II. Two friends of his, a pair of brothers named Rick and Nathan Lang died on November 14, 1942 in the Battle of Guadalcanal. Although Leo saved many men that day, he felt guilty about being unable to save his own friends from getting killed. Leo died later that same day, while bandaging a soldier's head wound. Later, while pretending to be his own grandson, he encountered that soldier again, now an old man, who survived as a result of his actions and was very grateful to him. Upon his death, Leo was woken up and was surround by the Elders, who offered him another chance at life, by being a Whitelighter.
He was close with another Whitelighter, Natalie, who was in Whitelighter training around the same time he was. Ironically, the two were both Medics in World War II, while they were both humans. They quite possibly became Whitelighters at the same time.
In the late 60's, Leo befriended Penny and Allen Halliwell, the grandparents of the Charmed Ones, and would openly practice Magic with them and other Whitelighters in the manor. He was visited then, by a future Paige from 2004 who was transported by putting on Grams's red Go-Go Boots, which had a spell on them which returns them to the Owner, which was a past Penny. Unknown to him who she really was, he would often flirt with her, offering "Private Lessons", Paige who was disgusted by this turned him down.
During the mid-late 20th century, Leo tried to hunt down and kill a powerful Darklighter called Rennek, who was killing several magic practitioners. After he apparently vanquished Rennek, The Elders rewarded him with the task of being the guardian angel of what would become three of the most powerful witches in history.
Whitelighter of the Charmed Ones
- Chris: "What is wrong with you two? You're acting hopeless."
- Phoebe: "I don't know. I mean, I guess I always feel like this before a big battle, and then Leo comes down and I don't know how he does it, but he makes me feel like I have the power to do anything."
- Paige: "Really? It's different for me. It's like I forget that I even have any training and Leo helps me focus and calm down."
- — Phoebe and Paige talking about Leo[src]
Leo was sent by The Elders as the Whitelighter of the Charmed Ones. Because he wasn't supposed to reveal himself as a Whitelighter to them yet, Leo got a job from the sisters as a handyman fixing up their old house. Phoebe and Piper immediately became attracted to him. As Leo worked on their house, Piper and Phoebe competed for his attention. Piper invited him for dinner at Quake to look over stain samples to refinish the wood in the house.
Although Piper and Leo started dating and consummated their relationship, he had to leave her because relationships between witches and Whitelighters are forbidden. Before Leo left, Rex Buckland blackmailed the Charmed Ones into giving up there powers by casting a relinquishment spell from the Book of Shadows. After it was cast, Leo found the Book empty and held his hands to it, restoring the book and the sisters' powers. Piper then froze the warlocks, allowing Prue to move them in front of each other, causing a shapeshifted Hannah to maul Rex and kill him. She was then vanquished by the Source of All Evil for failing him.
When Leo returned, Phoebe then discovered him using his levitation to change a light bulb and he confessed the truth to her.
When he later got injured by a Darklighter's poison arrow, attempting to protect his charge Daisy, Piper learned he was a Whitelighter, much to her initial irritation. Piper used a spell to switch powers with Leo, so she could heal him while Phoebe and Prue protected Daisy and vanquished the Darklighter. Although Leo offered to give up being a Whitelighter to be with Piper, she didn't want him to give up his calling.
When Piper went to a possible future in 2009 with Phoebe and Prue, she learned that she and Leo were divorced, and they had a daughter named Melinda Wyatt.
Piper tried to move on, and started a romance with her new neighbor Dan Gordon.
The Elders have a rule of not healing when the injury/disease is not caused by a demon. Leo broke that rule when he saved Piper from a deadly disease. Because of that, Leo was suspended from being a Whitelighter for at least three months.
Marriage to Piper and their family
Leo eventually earned his wings back as well as Piper's heart. He asked Piper to marry him when they got back from the Whitelighter Dimension.
A warlock named Eames was killing many witches and other supernatural beings to reach his great goal. A Whitelighter named Natalie went to Leo and the Charmed Ones for help. Phoebe had confided in Leo that she didn't really vanquish Cole. The Elders were so happy with the Charmed Ones performance against Eames that they lifted their probation on Leo and allowed him to be engaged to Piper.
The ceremony was performed by Grams, and the Elders allowed Patty Halliwell to return for one day to witness her daughter's wedding. The ceremony was also attended by Phoebe Halliwell, Prue Halliwell, Victor Bennett, Cole Turner and Darryl Morris. Although the marriage was considered legal in the magical world, it was not in the mortal world, due to Leo and Grams's status as being legally dead.
Piper persuaded Leo to attend the Guadalcanal reunion under the guise of being his own grandson, Leo Wyatt III, after Leo faced up to his own guilt over Rick and Nathan's deaths, his faith in his decision to leave Rick and Nathan to save others being reaffirmed when he met all the men whom he had saved prior to his own death, along with the families that would never have existed if it weren't for Leo's sacrifice.
Soon after, Piper became pregnant. Leo and Piper had their powers swapped by their unborn baby for a short time, until they learned to appreciate how hard each other's life is. Piper gave birth to their son, who she would eventually name Wyatt Matthew Halliwell — with Wyatt after Leo for being a very protective father, Matthew after her half sister Paige, and Hallliwell of course being the family name.
When Piper and Leo's arguing began affecting Piper's powers, Phoebe suggested that they visit a marriage counselor. Piper cast a spell that allowed them to relive the good and difficult times during their relationship, which reminded them of why they got married. But as well as reaffirming their relationship, the session allowed them to realize that they had issues to work out.
Leo's marriage to Piper was turbulent, especially when he became promoted to an Elder after saving them in "Oh My Goddess".
Leo as an Elder
Leo was later promoted to be an Elder and had to leave his family behind. However, he managed to watch over them, especially his son, as he was given rights to visit him. However his appointment cost him his marriage to Piper. Chris Perry, the Whitelighter from the future, had taken his place as the Charmed Ones' new Whitelighter.
Since Piper and Leo's parting, Piper had become increasingly happy. Alarmed by her change in attitude, Paige and Phoebe told Chris to ask Leo about Piper, but Chris admitted that Leo had been kidnapped. When Paige and Phoebe told Piper that Leo was missing, she was oddly unaffected by the news, not really remembering their parting. But when the sisters finally found Leo, Piper's memories came flooding back. She demanded to know why she did not remember Leo leaving her, and Leo told her that he used his powers to make her forget and not feel as much pain. Not wanting to face the pain and anger she felt toward Leo, Piper became a Valkyrie. Phoebe and Paige confronted Piper, using a spell to make Piper feel her suppressed emotions. Once confronted with her pain, Piper realized that she did not belong with the Valkyries and returned home. Leo apologized to Piper for taking away her feelings. Piper said that she understood that he was only trying to help, but she told him that since he was still an Elder she would appreciate his keeping his distance so that she might move on with her life.
Even though Piper tried to distance herself from Leo, she realized how much Leo missed Wyatt and how much Wyatt missed his daddy, so she told him that he could visit as much as he wanted when she was not around. But much to Leo's disappointment, Piper asked him for a divorce when she started to date again. As an Elder, Leo was not allowed to live with his family, though he promised always to watch over them. However, Leo had serious doubts about the mysterious Chris, and he stayed involved in the family's life as he tried to figure Chris out.
When a demon used the power of a genie to wish the Charmed Ones dead, Leo's connection to Piper saved the sisters. Even though he and Piper were in a magically-induced sleep, Leo heard Piper's cries for help when her spirit began to move to the afterlife and he healed her. This incident drew Piper closer to Leo, as she was reminded of her connection to him.
After Leo and Piper were trapped in the Ghostly Plane, the two had a moment and Piper got pregnant with their second child, who happened to be Chris. When Leo finally found out that Piper was pregnant again and Chris was their son, he decided that his place was to stay with his family. When it is revealed that Chris is actually Leo and Piper's second son, Chris admits that Leo was always there for Wyatt, for the Charmed Ones, but never for him, as he was often eclipsed by Wyatt's "Chosen One" and ultimate power status. Chris's presence in the past, coupled with his unerring dedication to saving little Wyatt from the evil that corrupts him, helps them mend the relationship.
Trying to absorb the situation, Leo took his time in approaching Piper about the impending birth of their son and the future of their relationship. While Piper admitted that she thought about them becoming a family again, she tried not to because things had not changed — Leo was still an Elder.
When Leo learned that his mentor Gideon was after Wyatt and that Gideon had killed Chris, Leo avenged his son by killing Gideon, using his powers as an Elder while working in conjunction with his evil counterpart from a mirror universe. Leo also realizes that Barbas had cornered him and made him live his worst fear — killing an elder and the older (evil) Wyatt killing him. He realized that Barbas must have been working with Gideon. While he has lost Chris, he still has the opportunity to save Wyatt, and goes after Gideon, killing him and saving Wyatt from becoming evil. Baby Chris is born later the same day, Leo returning to be with his family once more.
Unfortunately he was also haunted at the time by his loss of Chris and because of that, he'd been hunting for Barbas since he teamed up with Gideon to kill Wyatt in the Underworld, plus he and the Charmed Ones also found that Gideon was not the only Elder who felt that Wyatt may turn evil. Leo had accidentally killed the Elder, Zola, who once tried to reach out to Leo to help him.
Leo was not trusted by the Elders, however, he had to return to his status, to prepare for the "gathering storm" of a "new power". Unfortunately, he and Piper had planned for him to move back in with them, but he felt that he was too dangerous.
Leo as a Demon
This Leo wore a mask that hid his face but resembled Leo exactly. After Grams and the real Leo see the demons face they believe that Leo is evil and that some of Leo's feelings about Wyatt's existence manifested itself into a demon. The real Leo goes to a demonic Seer to determine where the demon originated from and Leo and Victor and Patty conclude that Wyatt accidentally created him. Victor and Patty remember when Piper was little she had night terrors over her parents divorce and that it was her subconscious way of blaming herself. Since Wyatt is so powerful however he brought his nightmare alive since he blamed himself about Leo not being around all the time and Piper wanting to divorce him after saving him from dying at the hands of Gideon. In Wyatt's mind if he wasn't alive everything would go back to normal.
Demon Leo takes Wyatt to the spot where Leo killed Gideon and attempts to get Wyatt killed by other demons but Piper and Leo arrive just in time and vanquish them. When Leo explains to Wyatt that he and Piper did not break up because of him, Wyatt makes the demonic Leo go away.
Leo as An Avatar
Later Leo was convinced to join this new power, the Avatars, in the hopes of being able to give himself, Piper, and the sisters the demon-free normal life that they were now craving. He later informed the Halliwell sisters of his new status, following which he became a target for Kyle Brody, who wanted revenge on the Avatars for allegedly killing his parents. However, after he and the Charmed Ones, in spite of Brody's best efforts, helped the Avatars create their Utopia, Leo was soon made aware that the world the Avatars had created was not as nice as he'd envisioned due to loss of free will. To convince the sisters, Leo sacrificed himself by getting angry and vanquishing a demon, thus forcing the Avatars to erase him (as they did to all who still caused any conflict). As he was dying, he relayed a message to Phoebe, who remembered, and then took it upon herself to make sure her sisters felt pain in order to see that what the Avatars were doing was wrong. The sisters, realizing Leo was right, confronted the Avatars. Time was then turned back to the point before the Avatars changed the world, and Leo was restored, although his Avatar powers were stripped away and he became an Elder again.
The Elders were left with the question of how to punish Leo for becoming an Avatar. After weeks of debating the proper punishment, as a test to see what Leo's destiny really was, they finally decided to relocate him on Earth and take away his memory. The two Elders representing the Council of Elders were Odin and Sandra who told Leo that he would somehow find his way back and choose between rejoining his family and becoming an Elder full-time. However, Odin felt that Leo's rightful, proper place was amongst the Elders so he cheated on this test and tricked Leo into rejoining them by infiltrating the test appearing as a truck driver. At this time, Piper was dealing with an infection from a Thorn Demon and was trapped in the Cosmic Void only being able to be saved emotionally by Leo.
Phoebe and Paige confronted Odin and Sandra about this atop Golden Gate Bridge. At the same time in the Void with Piper was Cole Turner who urged Piper that she needed to let go of her life so that Leo would receive a psychic shock and feel Piper's love for him. Piper decided to trust Cole and she let go of the life she had, as she dies she calls out for Leo. Leo heard her call for him and chose to "fall from grace". Leo thus gave up his powers and his Elder status and became a mortal human, but he got his memory back. Leo then returned home to Piper and their two sons. Thanks to Drake and Wyatt, Piper survived as Drake was able to have Wyatt heal Piper's wound.
Headmaster of Magic School
Piper and Phoebe decided to have Leo become the new headmaster of Magic School, letting Paige go out into the world and try something new.
Leo "died" with the Halliwell sisters, adopting the name of Louis Bennett, but soon got back to his old life and name.
Leo and Piper went to a magical marriage counselor, but things did not turn out as well as they had hoped. Their counselor needed them to see how each of their lives was in order to get them closer to each other. In order to do this, the marriage counselor had them switch bodies in order to walk a mile in each other's shoes. This made them work out the problems, although Piper disagreed on seeing the magical counselor whom she called a yahoo.
The series finale and the future
In the last season of the series, Leo was the target of the Angel of Death. The sisters searched for a key to undo his death sentence. Piper summoned both an Elder and an Avatar to give Leo a new lease on life, but both were forbidden to do so. In turn the sisters summoned the Angel of Destiny, who warned them of an impending great evil force, that Leo's death would be the only motivation to give the sisters the will to fight the great evil. So they decided to freeze Leo promising if they beat the great evil, he would be returned to them.
After the destruction of the manor and the deaths of Phoebe, Paige, and Christy Jenkins, Leo was returned by the Angel of Destiny. Had he not intervened, Piper might have killed Billie Jenkins in an act of revenge. With the manor destroyed, Leo and Piper left the area.
Piper and Leo went back to the past to fix the present, and saved the future so that Phoebe and Paige live. After they change the past in order to let Phoebe and Paige live, Leo is returned to the sisters, and Piper more importantly.
In the new future, Piper and Leo have a daughter, Melinda Halliwell, and Leo returns to teach in Magic School. In the end of this episode they finish the Book Of Shadows by writing about their lives so all the generations after them would be prepared to fight demons, warlocks, and other bad guys. They may not have been fighting demons forever, but they certainly were...Forever Charmed.