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. Head over there and enter the castle and see if they are in there. Now talk to a lord in your faction and find out where the ladies are. You also want to learn any poems from the bards, as we need A Heart's Desire. For example I had -3 with a girl's relative, but it didn't say anything about him disliking me in the notes section. If you go to notes > characters it only tells you their relations if it's high or low enough. Can't really check their relative's relations without tracking them down and holding LT though. You can check this under notes > characters, find her and select her to see her relatives. In order to elope her relatives need to dislike you, or at the very least not like you. You'll also need to make sure you don't have good relations with their relatives. 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.

So just stick to romantic ladies for this. When I did it with a romantic lady, I was given the persuasion check at 14 relation. I had a conventional lady at 40 and couldn't elope, nor was I even given the option to pass a persuasion check. 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. 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). Next you want to talk to one of the bard type NPCs that appear in towns, like wandering ashik, troubador, etc. Garrison some troops in it and the enemy will generally leave it alone for easier targets. Once you have it make sure you don't lose it, obviously. 95% of the time the king will award it to you. Take a castle or town yourself and then choose to ask for it. The simplest way to do this would be to get 150 renown and ask a king for a fief. The first thing you want to do is get a castle or town. 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. It appears this can only be acquired as a male.

Mount and blade poems