I only have one sister-in-law. I don't think we would naturally drift toward each other to become friends if we were placed in a random group of 100 people. We are not very similar. But, if we were randomly thrown together as housemates or next-door neighbors or co-workers in a small group, I think we would become good friends over time. She is a really great person and I admire a lot of things about her. Also, I enjoy schmoozing with her about the things we do have in common.