There is a max limit of 4 children per guy, including adoptions, unfortunately...

BTW, I've made a little tweak to princesses, I added +3 charm to the "IamPrincess" trait(hidden one to name her as princess), and also included the extra triggers for princesses traits kobal2f has in his mini-mod. This way, most princess start off with 5-6 charm, and they are now as beautiful as a princess should be! at least in my filthy imagination, that is...