Makes sense. I know bona fide mental illness (like the kinds with names that can be diagnosed and medicated) can run in families and can give a person a predisposition for developing the same conditions, but it doesn't surprise me that a person can be an asshole and pass those traits on via nature rather than nurture. In this case, the douchebag father was nowhere near the kid, so it wasn't his influence doing it. The kid just went bad.
I would love to know what precisely this woman saw in the guy that made him worth getting to know well enough to fuck. Because unless he was rich or enormously endowed, I don't see anything fuckable from her description. Now she has a monster who has zero empathy, enjoys hurting others, doesn't listen to anyone, and Moo has to pay him to spend time with her daughter because for some reason, the younger sibling is over the moon for her older brother that does nothing but insult her and steal/break her toys.
Sounds like Moo has done lots of damage by reproducing with a prick, not only breeding a replica of the asshole she left, but raising her daughter around this asshole who will likely grow up to believe being mistreated by men like this is totally normal, making her prone to dating abusive men/women. Yes, she should have absolutely aborted. But given how the kid acts, it might not take long for someone else to abort him. Because mark my words, he's gonna fuck with the wrong person and they won't be afraid to lay him out or blow his head off.