Imagining an alternate family is a creative activity that likely has its roots in childhood. I can remember, after getting spanked and sent to my room, cooking up fictional parents who never got mad and siblings who willingly shared their toys and never squealed on me. Somehow, those new relatives always closely resembled my actual family, but with the rough edges removed and idiosyncratic quirks added. Sometimes I would imagine my father as very tiny, and my brother as a rabbit. This imaginative play has continued in my creative practice to this day.
Don't get me wrong, I love my family dearly, but my tendency to think of my odd cast of characters as family has advantages. Establishing characters based on actual people allows me to readily insert them into stories drawn from real experience and history. Although heavily fictionalized, this connection to lived experience, however filtered, lends the work a portal through which an audience can access the familiar. Given that my work is also loaded with and defined by a sense of dream logic, this thread of reality helps keep the narrative from floating off completely.
I can't know about your family, but my guess is that, like mine, it is filled with odd ducks and goofballs, storytellers, liars and performers. Being part of a family is heaven and hell simultaneously, and thankfully, keeps life interesting. Like my wife Jennie always says: "Friends are great, but blood is thick."