What is family?Watch
From what I know, family is based on genes, culture and society.
We're all related but I'm not "allowed" to call you or any other the other animals/living beings my family because society and possibly culture says that your family is those who share common DNA with.
I don't think that everyone you are commonly related to is family as you don't have a relationship with ALL your relatives.
I don't class my one cousin's children nor most of my "family" who are on my parents' side as my family as I barely see them, they're strangers to me. No relationship=No family.
My mother thinks I should as "Family is family" but I'm not allowed to regard my the same cousin's mother who I've never met as my aunt. I don't get it.
I do regard my best friend as family, she's like the older sister I wish I had.
I've seen on The Flash that they all regard each other as family so I guess it can depend on the person?
It's when you're birds of a feather and have high hopes for the future.