List of Possible Familial Relationships

This is the list of possible familial relationships which appear in Phineas and Ferb.

Isabella Garcia-Shapiro
Major Monogram might be Isabella's father or stepfather, in actual Danville universe. Monogram's wife is all about Mexico and stuff. In "Doof Dynasty", Major Monogram is also depicted as Isabella's father. However, Isabella met Major Monogram many times without mentioning that he's her father.