I love relative crossovers. Mostly the 'extened family' kind. I don't like the "hey, this is the sister I never talked about- let's watch her win the hearts of everyone and then kill the Wraith" ones.

But, everyone has cousins and such. Richard Woolsey? He's related to the Weasleys. When his grandfather came over, they changed the name. Lorne is not related to the Winchesters, but his father was friends with their father. Lorne spent some time with them growing up. They told the best ghost stories. Chuck has a crazy Uncle Frobisher. They don't talk about him much, nor is he invited to the chili cook off.

And these are the stories I'll never write. But it is fun to think about.