Friend-in-law

I went slow cooker shopping with a friend, who's not really a friend. We know each other from mutual friends, we've seen each other at various things from said mutual friends and I used to run into him when we lived in the same suburb. He described our relationship very aptly: we were friends-in-law. Possibly friends now, after having bought slow cookers together, but I like the phrase: friend-in-law.