Letting the PC have kids is probably not a good idea, because in general, we want to adventure, not babysit kids

.
As for a wfie - well, probably not a good idea either. While I'd welcome the possibility of a romance, chances seem low. Maybe you could become engaged to certain people, but the only effects of this would show up in the ending.
I still think that the best we can hope for in this regard will be something along the line of the http://fallout.wikia.com/wiki/Bishop_Child (which would be cool IMO

) .