Cherrybim,
Take a look at the medrash rabbah(very beginning of brashis or shemos(or one of the other 3 chumashim)) where the parenting mistakes of the aforementioned avos are laid out. It doesn’t mention that they had split personalities, but as PBA mentioned, some children need special treatment without which they will end up in trouble. But, not every child of a parent who is unsuccessful at parenting will necessarily end up in trouble.
So, therefore, it could be that avreham and yitzchak made mistakes (dkei dakos ones for those with slabodka leanings) and contributed to their childrens eventual sins, while NOT having split personalities.