My mum and my 'aunty' have been best mates since they started school at 5 yrs old, 52 years down the line still best mates! I only found out about 5 yrs ago (when i was 15) that Aunty Sue, was actually not my aunty and uncle Alan was not my uncle :( But to me and my brother and sister, they are still very very much Aunty sue & Uncle Alan, and their 2 kids are always known as cousins :)
I was born next to my best mate, went to playschool, nursery, junior, primary & secondary school together! Now shes at uni & im working, dont see her as much as i would like, but she is always always there for me :)