Gordon Johnson II is only mentioned in the tree. His existence is disputed by Penny's statement about Wyatt Halliwell being the first male in the Warren Line of Witches. However, he may have been born without powers, and thus not counted as a 'witch.'
The family tree indicates that Francine was born in 1879 and died 1956. This means that Gordon would have been 64 years younger than his proposed wife. This is possibly a mistake on the part of the family tree, or the prop masters of the show who created the actual prop.