Things get a little shady when you figure out that you can go full Mormon and propose to just about any NPC you happen across, and if you have the inclination you can start up different families in every town dotting the game's open world. Making that scenario happen takes about as much work as you'd expect, and if you don't keep any of your spouses' "happiness ratings" up to acceptable levels, they may start regretting their decision and ask for a divorce faster than Tom Cruise's next church-approved wife.
They also may even start cheating on you, but did you happen to read the whole description of requirements for the "Paramour" achievement? Yes, you could always try to save the marriage and spice up your love life by having a friend watch while you play "where'd that pesky pickle go?" with your beloved. Alternately, you could kill two birds with one bone (I'm not apologizing for that joke) and work on "The Swinger" achievement simultaneously, by dragging them both along to an orgy with those aforementioned prostitutes.
Microsoft Game Studios
Who ever said Feudalism wasn't a party?