You have these people in your life who you really aren't friends with. .. But because of there connections with other people in your life. .. You friend them to kind of look out for the interests of a family member. For example I have no reason to be friends with my sons ex girlfriend. She Just friend requested me and I was hesitant, but then I thought. .. Well maybe I could observe for my son. I did let her know up front since she immediately messaged me that if she tried to use me to get at my son. .. It wouldn't work because I would always have his interests and side first so don't even try it.