There's an old quote "you can choose your
friends but you can't chose your
family".
Most people have close
friends that they consider family, someitmes even closer than actual family members. They call them their other sister, brother, aunt, uncle, cousin or parent.
Your friend marries a member of your family.
Your best bud is like a brother to you.
You consider your bff a family member.
if you're closer to your
best friend than you are to your family members, they are your "friendamily"
Your children call your close
friends Aunty and Uncle even though they are not related.
You have people that you think of as your other family members though they are not related. eg. You call your
friends parents Mom and Dad.