Just another thought; remove all thoughts of incest, replace GA had a gambling problem which put house hold into serious financial straights. He said he would quit. Right after Caylee is born CA finds GA back to old tricks and says move, I can't support us and your habit.
When GA moves back in , he starts working PM because the money is better (shift differential). And there are fewer hours of day with no adult in the house.
LA is very angry with dad for financial problems and now for deserting family.
Even after C & G decide to get back together, LA hasn't gotten over being mad at dad, they were probably very close (L and G against C and KC) while LA was growing up. LA was (about) 22 when Caylee was born. A pretty
typical age for young people to move out.
Whatever problems KC has now, didn't happen overnite. She didn't plan on becoming pregnant, so she chose to ignore the situation. As long as she can deny, deny, deny she doesn't have to deal with what's coming next (a baby), 19 is kind of old for this behavior, 13 to 16 would be more common. Doesn't mean she was actively planning to toss baby at birth, these girls will go to the
hospital and deliver all the while deny being pregnant.
I'm not going to speculate on situation with birth father, there are too many plausible causes, ranging from KC really doesn't know (too many to choose from) to KC and CA actually know but he's not interested/doesn't know (married w\ kids).
I think this covers all your areas of concern and is easier on the brain.