Female soverign, married Janusk. I guess he's not picky?
I think that this was possible in the pre-release, but not with the Day 0 patch. In any event, I start asking NPCs to marry me as soon as I recruit them, and take the first one who says yes. Any benefit having a higher level NPC spouse might convey to your children is lost on me, since it takes too long to get children anyway.
Also, is there a way to check how much reputation an NPC requires before they'll marry you? Without actually proposing, that is?