[@Greenie] It'll have to be carefully worked out if you want to have a mystic character. Plus we don't know anything about Rhoynish water magic besides that they can control water and there is a religious element to it. Anything more is pure speculation. 

[@bloonewb] It's the 3rd Century, women can own property too y'know. 

On a serious note, I had that written in before Dredigan had Tyrion marry Sansa. I might have it rewritten so that one of Brandon's children is overseeing the land. But it would still make sense to have Sansa as the castle's steward. She doesn't have to be there all the time, and she's competent and loyal. Either way, the Starks have control of the Dreadfort for now. 

I imagine Brandon will probably keep the castle from the Boltons until they can prove themselves as loyal vassals. Or he might give it to another House that proves themselves. It's not so much that Sansa or whoever is the hereditary ruler of the castle now, but they are administering it for the time-being. Kind of like Moat Cailin or the Bloody Gate.