I stumbled across this game a few months ago and have thoroughly enjoyed it! I think Savin and the rest of the team have done an incredible job with it so far, so thank you very much!
Regarding the topic, I particularly like the idea of being a male character being able to father children from multiple characters in the game (or a futa 'father' works just as well!). The first time I played Tits, I was... confused, by the emphasis on the nursery at the beginning of the game and then the lack of options for potential mothers. Everything about the nursery setup implies a big brood of children, which doesn't initially seem all that feasible with a solitary female character.
I suspect that part of the reason this subject gets asked about so much, is because the intro to the game raises expectations which are then cruelly dashed! Alright, I'm exaggerating, but only a bit.
I've read about the complexities with writing code that have to take into account all the variables with an npc mother and it's really unfortunate that's the case. Briha and the Zil call girl are the only ones that I really count at the moment, in terms of actual characters rather than generic npcs that can be impregnated. The Saec addition in the sub-tuner sounds pretty hot, but I guess the ultimate fantasy would be to knock up the harem of girls on the ship. I believe that runs into issues with the crew being pregnant and ship-based combat?
As was mentioned above, a random npc just firing out 'x' number of children doesn't sound particularly compelling, but Reaha, Sera, Anno, Cerise, Yammi and the Pexiga all sporting baby bumps would be pretty damn hot! If not them, there's always the B team of... pretty much every non-recruitable female. ;-)
Ah well, a guy can dream!