It's weird, if most of the Humans have Saiyan blood in them, and they get married to a girl with Saiyan blood in them, their saiyan blood should increase..

That makes no sense.

Actually I came to a realization based on what someone else in thsi thread wrote. The reason Majins can not revert back is simple, Majin Buu and Kid Buu are two seperate individuals. The Majin race was created from Majin Buu, not Kid Buu. If you remember dbz, Kid Buu housed Majin Buu inside of him. After Goku and Vegeta ripped him out, they became two seperate individuals. Since they became two seperate individuals, Majin Buu lost the ability to revert back to his pure state.

Theres still more Human blood though.Maybe Human blood is more dominent when it comes to newer generations.

It would only increase if one of them had more Saiyan blood than the other. Otherwise it will stay the same or decrease.

that was super buu,and super buu transformed into kid buu after that (and since super buu was part of the normal buu normal buu could do that too)

Majin Buu can also become pure if e released whatever Kai DNA left in him.