The relationships people build with others can tell you a lot. For that matter, so can the way they perceive those relationships. Based on the candidate's account, how do they see themselves, and what do they value in others? You'll also get some insight into your interviewee's self-awareness. Humor, unless it's sarcastic and demeaning, is always a good sign. If the relationship they describe sounds too formal and humorless to be true, it probably is.