My wife's brother was being particularly obnoxious today.
I said to my wife:
Me: If he wasn't your brother, I wouldn't have anything to to do with him.
W: I he wasn't my brother, I wouldn't have anything to do with him either.
Me: Is blood really that thick? (Meaning: Are family obligations really so string that you'll put up with him no matter how bad he gets?)
W: Yes.