No, not "gotta be" incest. Incest could have contributed to the underlying tensions within the family.
Haven't seen the DNA tests.
Then, you've GOTTA go to the PR thread. If just for fun! You'd LOVE the DNA stuff! Because you have a quick mind.
Incest could have contributed tensions. So could having a chronic thief in the house. CA has had to plunder her 401K several times.
Plus the two dominent family members both have personality disorders. Which is a source of endless conflict.
Plus GA doesn't work much, and between his gambling problem and KC's thefts, the two nearly bankrupted the family.
So, they have a couple of mortgages, and had to borrow money on the house to pay bail.
And, now KC is an internationally known child killer.
And, thanks to CA and KC, they no longer have any family support.
RP used to post here, and on Topix. It was kind of sad. He said CA is the youngest sib, and the only girl. He and his brothers love her. But, there's an irreparable fissure, because CA won't deal with KC in a way that the family can accept.
That's prolly enough for family tension.
And, I think implying that RP may be a criminal is way off base.