There's another axis along which all lords are separated: Honorable and Dishonorable. I'm fairly certain this plays a big part when proposing marriage. If you're an honorable character and you're proposing to a dishonorable one, it wont work. In fact I suspect a few of your tests like the Upstanding or the Military ones may well have been tainted because of opposite honor standings. As far as how you establish who's honorable and who's dishonorable, I've only ever found one way: The honorable characters commend you on your chivalry if you release an enemy lord after defeating them in battle. The dishonorable ones will call you a twit.
