What a lovely story, brigidmac!
In my childhood it was common to call my parents' friends Uncle or Auntie, so I grew up thinking that I was actually related to them all. It took an interest in genealogy to sort out which ones were related and which were not. That kind of naming created a group of people who were not related, but who were closer than just acquaintances, a third tier of relationship, if you like. Nowadays, of course, youngsters just use forenames quite freely and this kind of quasi-relationship doesn't exist.
My friend's parents who were not in the Uncle-Auntie group, were politely given the titles of Mr and Mrs.