I've been creating fake people in my head since I was 6
That's very sad. What fake people are you creating, like fake friends or something worse?
Like literal fake friends, even fake parents sometimes. I've even created a fake teacher.
Having imaginary friend when you're young is fine but what you're doing is a bit concerning. You're an adult and by now you shouldn't really have imaginary friends, much less an imaginary family. I think you might need to talk to someone about it.
I lost a lot of people in my life, I just miss them.
If you have lost a lot of people in your life, it is okay to mourn and miss them, but you are disrespecting them if you are replacing them with fake people in your life. I suggest you end what you're doing and get more real relationships with real people.