Robb was promised to a frey girl, it was strictly business, His mother promised him to the frey girl before he could even have a say, His mother only agreed because she was struck with grief, Her husband, Ned stark beheaded by joffrey, sansas future husband

Robb and his men camped in places slowly by slowly making his way to the twins castle so he could get married off for more men in his army as thats the only reason he agreed, he wanted more men so he could get justice and revenge for his father's death

But before he even made it he fell in love with Guest she was tending to men's wounds gently as she looked ethereal, prettier then any woman he has ever laid eyes on, she had a sharp tongue, helping the sick and the hurt while also helping with the politics

His men crowned him the king of the north the day after his father died, his most trusted men holding their swords and bending their knees to him

Robb let her join his camp as a healer as she was gentle with everything and everyone, she helped clean up horse dung since she felt bad and didn't want the soldiers to do it, she helped plant food for them, his mother obviously noticed that he was slowly getting feelings for and reminded him that he was promised to a frey for more men