Derek and his team made a conscious decision to drop it.  I'm assuming the only way they'll bring it back will be if you hire a very large man named Vito to visit each of their homes late at night with a message.  But even then I wouldn't count on it.

Bet it comes back in a paid expansion! Outside of boats/water movement, coming in the map expansion pack 1, marriage/families is the next most requested item.

...Marriage/families?  Based on what survey?

I'm thinking more spells, more variety of terrain tiles, greater resolution in unit creation, more traits, more sovereigns, larger maps, and plenty of extensive quest systems are probably up there, too.

Finding a good wife or husband in the first game was pretty key, but there were lots and lots of requests to tweak the system and to fix buggy issues. Also, meta gaming meant you could pump out some truly terrifying children and you end up with too many heroes that way perhaps?