Board Thread:General Discussion/@comment-24098614-20161225210929/@comment-4010415-20161225212712

Goodwitch: As we understand it now, when a Maiden dies, the one who is in her final thoughts is the first candidate to inherit her power.

Qrow: Unless it's a dude or some old hag. Then the power goes to someone random, and our job gets a lot harder.

^ Quoted directly from Fall, during the "We're explaining the Maidens" exposition scene.

So, basically, only young females get the powers. Naturally, at least. There's no telling what happens if someone sticks a guy in the Aura transfer machine and puts a Maiden's soul/Aura into the guy.