Apparently you can marry/impregnate lots of the girls, I have not personally pursued that path as I concentrated on family members and tried not to do anything that would damage my familial relationships. I have played thru 5 or 6 times already and latest playthrough married all family members with Mom pregnant. 1st playthrough I only managed to succeed with Rachel. Seems 75% of choices in every relationship are critical to success. An excellent story overall with tons of replayability