Stormbringer is going to do what's good for her Holding. Right now, she's collected a lot of Selkie part-bloods for her own reasons, and the thought that Turnspit might have Selkie blood is making her calculate.

Well, funny you should mention being a relative...

Not really; it would be beyond her traditional authority, though she could push. She can certainly forbid Turnspit to breed with any of her people, as the Brewster did. She could also say 'only these people, but not these'. She is winding Iros up a bit. Pay attention to how *he* is acting around her.