The dad Vosseler, while totally selfish and cruel to Ruth, seems insanely intelligent. To orchestrate and execute all of these steps, aside from being wrong it’s like, who on earth has the time to think of all that?
Ruth seems highly intelligent as well.
CJ and Billy are IMO probably noticeably intelligent men. People will know them as “that really smart guy”. They’re probably also noticeably quirky from being raised by a father who clearly had a zany (at best) world view. But they might not carry overt signs of trauma because everything might have made enough sense to them within the “reality” that their father crafted. They may thus not be wondering who they “really are”.
When parents tell their kids falsehoods, those can seem real well into adulthood. One of my parents and their siblings didn’t realize how obviously untrue (like impossible) what they had been taught was until a good way into adulthood. Because it was accepted as truth when they were young, because it was what their mom told them.