First the Miller parents are both dominant, so their children were bound to become dominant too.
Actually it's pretty simple: The dominant alpha children manifested too early, with the exception of Chase who manifested late. And Chase was actually on the way becoming like Ashley, frying his brain because of pheromones. And he also isn't really normal.
When they manifest too early they have problems undertstanding/feeling emotions (that was mentioned in the Kiss me if you can novel) etc. And 4 of the 6 Miller children manifested before they were 5 years old/born manifested. Grayson for example is a born manifested, which makes him stronger than a normal dominant alpha.
The parenting wasn't really that good either, too many children, too many too early manifested, a jealous dominant alpha parent who also hated dominant alphas (trauma from his parent relationship). Ashley tired to help his children, in some parts he succeeded, but it wasn't the treatment they really needed which you will see with Grayson.
Yes, "Lick me up if you can". They fall in love as teenagers in highschool, when they are still not manifested and are like betas. That story also has a big time skip, so it kind of has two parts. Children and parenting are only in the extras.
So far it's novel only and there are currently no plans for a manhwa adpation, but if the opportunity arises the author will do what she can to make it possible.

I'm really curious about the miller parents. How did they end up with psychopath children