This system was not originally planned and it is too complicated to make it. But it may be added that pregnant NPCs lead to the opening of new characters over time
that one would be nice as well i know how a cc could be to advanced if its not a pre built system but id suggest you maybe look into making it for your 2nd game
but a simple unlock system could be nice as it would help people use their liked charters
id maybe suggest after you made this game either make a remake of this game or make a new world and add the systems i mentioned having the ability to populate the world could be really cool as it means you could spawn huge amounts of npc's and mate them
might be abit messed up unless theres lore about anyone being bred from birth is just a spirt over blood meaning not related
idk really how you would get past that
hmmmm maybe a corperation rules the planet anyone who you give birth to is taken and replaced with a random slave from their stocks this means when you or your mate gives birth the corperation comes down takes your kid but replaces them with someone random
we are basicly just breeders and breedies pumped with pure desire chems to make us want to breed each other
this is the only way i could see getting around the kinship