User blog comment:American che/The Genetics Behind Phineas and Ferb (actually quite interesting)/@comment-844113-20100317220830

I had a feeling nobody would really understand, haha. It's seventh and eighth grade science.

By the way, Cain is a fanon character (he's never appeared in the series; I know because I've seen every episode ever released) and therefore Fred could not be Cain's kid. Whilst discussing this in my class with two other friends, we got so frustrated that we called the whole thing off and classified Fred as a genetic anomaly.