Mount & Blade: Warband

It appears this can only be acquired as a male. Thanks to Infamous for telling me this!

This is kind of like marrying someone, but the main difference is that instead of getting her relative's approval, you say fuck them and get married anyway. The first thing you want to do is get a castle or town. The simplest way to do this would be to get 150 renown and ask a king for a fief. You'll be a part of their faction now. Take a castle or town yourself and then choose to ask for it. 95% of the time the king will award it to you. Once you have it make sure you don't lose it, obviously. Garrison some troops in it and the enemy will generally leave it alone for easier targets.

Next you want to talk to one of the bard type NPCs that appear in towns, like wandering ashik, troubador, etc. Ask them about each eligible maiden and make a note of which ones he describes as romantic (EDIT : I'm playing the WIN10 version and I was able to get it with a woman that was "wild and likes to ride" or whatever, this seemed to be easier for me because these women were more likely to show up to feasts than romantic women). Ladies that are conventional or moralistic either require ridiculously high relations to elope, or won't do it at all from what I can tell. I had a conventional lady at 40 and couldn't elope, nor was I even given the option to pass a persuasion check. When I did it with a romantic lady, I was given the persuasion check at 14 relation. So just stick to romantic ladies for this. It said 20 relations was the cut off, so if your persuasion sucks you'll have to build your relations with her more than me. More on that in a second. You'll also need to make sure you don't have good relations with their relatives. In order to elope her relatives need to dislike you, or at the very least not like you. You can check this under notes > characters, find her and select her to see her relatives. Can't really check their relative's relations without tracking them down and holding LT though. If you go to notes > characters it only tells you their relations if it's high or low enough. For example I had -3 with a girl's relative, but it didn't say anything about him disliking me in the notes section.

You also want to learn any poems from the bards, as we need A Heart's Desire. Now talk to a lord in your faction and find out where the ladies are. Head over there and enter the castle and see if they are in there. If they are, skip the next paragraph.

If they aren't, you'll need to wait until there is a feast in the castle they're in and then they will appear and you can talk to them. If you don't have enough renown you may not be able to join the feast unless you win the tournament. I think the cutoff is 200 renown.

Start off by saying you admire them. If they're in one of the big towns, win a tournament and dedicate it to them. That's all you can do now. Now you'll have an option in the town to try and see them. Generally if you wait 4-5 days you can (a nurse will offer to take you in) but if you wait a week the lady will summon you. Once there, choose poems and use A Heart's Desire to get more relation. I had 9 persuasion and was able to pass a check to ask her to marry me immediately, and then when she said her family didn't like it, I asked to elope and she said yes. If you don't have enough persuasion you'll need to get more relations. If you wait until she invites you and head to her, you'll get 1 relation. You can also try other poems, though be ready to quit out and reload your save if they lower relations. You can dedicate more tournaments to them, but it only seems to give a big boost once. One last note, it's possible another suitor may take her, if that's the case tell her you'll duel them and then go beat them in a duel, or you are fucked.

Achievement unlocked for me during the wedding scene.