Self, one reason the court apponted psych recommended my Paranoid Personality Disorder ex wasn't allowed any direct contact with our two kids, was because there is evidence there might be a slight genetic predisposition for these things - but if children are not exposed to it constantly in childhood, the chances are they will be mentally healthy, in later life.
I don't know if that's based on sound research but it was actually the argument used in court that meant ex got zero contact.
One of our sons is just essentially my lovely late dad, in another body. He seems to take totally after our side of the family - not just looks, but personality. The other is very like his birth dad, and I worry more about him, but tell myself my older kids turned into super decent human beings, so he has every chance...
Talking of a psychopath having to fake caring about a death in the family... My ex once said something that creeped the shit out of me. "If you died and I had to bring up the kids on my own, I'd tell them you had been a beautiful, golden haired angel". wtf? Who even has thoughts like that? And he certainly didn't treat me as if I was a beautiful angel - he treated me like a piece of shit. But the message was, if I was conveniently dead - he'd then confer sainthood...
One night I was driving back alone from somewhere, after he'd had an argument with me, and I had a very near miss (If I'd been on the road at the time he thought I was, there was a collision and I'd have been in it). I was so upset I pulled up for ten minutes to recover before I drove off and that saved my life.
When he found out, the next day, I got the distinct feeling he'd have told everyone - including my kids - that it was my fault as I'd driven off "in a temper" (A remote country lane, and someone coming the other way skidded right across to the side of the road I'd have been on, and killed himself). They'd have thought that of me forever and he'd never have told them the truth. And he really seemed to enjoy the idea of being a single parent (martyred, maybe had pulling possibilities...) Totally emotionless, just a cool assessment of how he could get sympathy/money/screwed out of a situation. Even to the point he'd have made my kids think badly of me if something happened.
Oh and the first film he ever took our older kid to, was 'Finding Nemo'. I realised he loved it so much because the mother is conveniently wiped out in the first 5 minutes. Sadly his single dad fantasy never happened. Well, not sadly.