Regarding Mpreg, I've had men as mothers in my fics, but I don't think I've actually shown a male pregnant (not because it bothers me, but I just like to cut to the chase and have the kids already there.) My wife and I have had our male characters pregnant in our verbal RPGs, though. Seeing as 90% of my favorite pairings are same-sex, I wouldn't often write about families if I didn't enable men to be mothers or women as fathers.