I need help

My player (playing a high ranking guild member) would like to marry a noble lady from a minor house (she's pregnant with his child).
I've searched all the books and am still not sure how it would work.
The easiest way would be for him to become her lover (not husband) and the baby could be a recognized bastard child (some houses give almost full rights to bastards according to the books).
But the player wants the real thing
