I was just thinking today that I have exactly three family members that are (or were) also my friend.
My granny, who loved me more than anyone else ever had or could — she was my friend.
Her sister, my blind Great Aunt Margaret, also interacts with me as a friend.
I also have a distant cousin who I’d love to be closer to, both geographically and personally is a friend.
There have been some interesting socio-anthropological studies done, and theories proposed on the value of grandmothers.
Naturally acquired or otherwise, I think they’re just about the best thing ever.