I'm going to keep one trait constant in all the descendents, randomizing the others. My heirs will all be female, so I guess I'll have to have spare female siblings too. Oy, maybe not the matriarchal rule, haha.
I just reread the rules and as far as keeping the fathers around, since their LTWs matter too, I guess it must be worth it to keep them around. I wonder what people do when there are multiple mates to the same female sim. All under the same roof?