Reflecting on my own experience - frequency of contact (if I see them once a year, can't really count them as close friends) How involved they are in my life - are they people I turn to when I'm facing a problem, do they turn to me when facing their own problems? Do we have frequent deep conversations - not just surface level discuss the weather, sports etc. but stuff that matter. Quantifying this - length of friendship (# of years), frequency of contact (annually, monthly, weekly etc.), level of trust (low, medium, high - can I trust my kids with them kind of trust), level of involvement (low, medium, high - what things do I feel comfortable sharing with them - suppose this is also level of trust?)