I have had that brother-in-law for more than 50 years. I didn't pick him - my sister did. He is all kinds of good.
No.1 in my mind - energetic The guy has energy. Not just up and at 'em arm and leg energy but psychic, too.
No. 2 - genetic/biological energy He and my sister have made some excellent children and the fruits show. Those former kids are more than grown now. They have children of their own.
No. 3 - brains He became the family go-to guy for information on our ancestors. He knows more about who I came from than I do.
If you are considering brothers-in-law, look him up. He is a good template for shopping.