For now, no other men have appeared as potential rivals to either marry/and or have children with, so unless the MC meets another woman not already in the family, it doesn't look like there will be any pregnancies any time soon baring unforeseen or maybe not so unforeseen 'accidents'.
Logically the rules make sense, romantically, not so much as they have to practically live the Jedi code and not catch strong feelings since **feelingsbad**. I liked the initial premise of the story, but after reconnecting with his mom & sisters, it seems as thought the development has stalled a bit. As the MC is not allowed to pursue any real L.I. within the family, and nothing pending outside of it, it just seems limited in where the story can go from here by trying to apply real-world logic into a story that objectively speaking couldn't be more unrealistic.
I get the dangers of procreation run rampant, but that shouldn't prevent those truly already in love from being in an actual relationship, yet still open to sharing or being in a poly-relationship. I've said it before and I'll say it again, considering the resources available to the MC and the family, you would think there would an expensive, but possible genetic work around to the issue of bearing the MC's children as far as Rebecca and Suzy are concerned. IIRC, I don't think anyone else was as serious about marrying and having children with the MC.
/rant