Grammar correction: I still think it was funny that aliens wanted to keep abducting a merman musical genius at the top of the musician career branch.
Anyways, out of everything I read, I haven't seen anything that gives me confidence that he's immune from the impregnation because of his occult status. This is generally something I want to avoid. I did learn that a full household can prevent the alien pregnancy. A sim can't get pregnant if there is no room for the baby in the household. So, even if it wasn't planned, creating a family of sims and adding a few pets might help.