So males having sex with some women that are not related with MC at all, right?
No, there is so much more room for interesting stuff. Sharing, poly-relations, etc. Since we seem to be talking incest-heavy setups, here are some examples from that realm:
1) MC is insecure and sexually-inexperienced. His loving father convinces his mother that she should take her son's virginity, which she does. But obviously mom and dad continue to have sex with eachother, too (because they love each other, and their son).
2) MC has a girlfriend who had some point confesses that she has an incest-fetish (too). MC supports her, and she seduces her father. This shared bond intensifies the love between MC and his girlfriend. They marry. Her first baby will be with her own father, but then its MCs turn (who may be breeding his own family members in the mean time).
3) Variant on 1. We play as the father convincing the mother to de-virginize her son. In line with the new family tradition, dad gets to introduce the daughter to sex in turn. Either they now all fuck amongst each other in a loving family fuckfest, or they figure out that actually mom+son and dad+daughter would be the better couples, and so they just rearrange the family like that.
4) MC's sister is married/in long term relationship with a great guy, who gets along well with his brother-in-law. But the BiL is infertile, and eventually the sister turns to her own brother to get pregnant - with the knowledge and agreement of her spouse.
5) MC and his best friend make a plan where they try to seduce each others (single/widowed) moms with the hope to swap later. After the boys demonstrate to each others moms how great sex with a young stud is, they succeed (with some threesome-DP-action along the way).
I could keep going, but it would only frustrate me more.
