I like that you are so enthusiastic about the story that you have this vision for it. That said I don't think it fits the characters for it. 3 Generations:
Grandma - You have to remember that she was married to Winston from a young age and he was her first and vice versa, other than Winston, the only other sexual encounter she has had is with Baguette. She's very old school loyal and only libido motivated her to ask, it was a learning curve for her as well to discover people were more free, and rather disconcerting in the beginning for her to imagine that everyone was essentially as free loving as her daughter is.
Katelyn. - Despite being the opposite of her mother, and essentially turning any male or female (or futa) she encounters into a pincushion, she did inherit a little of her mother in that she only really fell for one man enough for her to get pregnant by him, she's not really gonna let another guy do that, or he'd have to be pretty spectacular to do so.
Roderick - Well Roderick is a guy, there are some works that go for male pregnancy and supposedly men can get pregnant these days if you read a Salon article. But for me I don't think him getting butt pregnant would work.
I think I did have a poll once about whether Stilyo could get men butt pregnant though, I'll have to check that again for the result to confirm. She might be able to go for Grandma and maybe Roderick if that was something supporters wanted, but Katelyn is a big no no for her. It's subtle but if anyone has watched my video series and knows that:
Then you can pick up on little signs such as:
So when they meet I will have a moment where for some reason unknown to them they dislike each other immediately, but I don't want to derail the story so I will leave it optional to explore that or not to the player. So those two WILL not be doing each other, or it will be unlikely they will.