Headcanon that’s not really a headcanon but it gives me feels:

Svetlana was the original personality. She was there first. Though, being born into a man’s body, she realized her transgender identity at a young age. Wanting to be a normal boy like everyone wanted her to be, Mike came into existence. The personality Svetlana’s parents had wanted. Svetlana had been given the name Mike at birth, but now she introduced a face for the name. She receded into Mike’s subconscious, choosing to live there, away from the expectations and pains of living in the real world. It was there that she began her gymnastic career, having an affinity for such a thing. Mike became convinced he was the original. Svetlana created the other personalities to keep her company. She based them off of things and people Mike saw throughout his life. Chester was Svetlana’s take on her grandfather, Vito parodied the Situation she saw on Jersey Shore one afternoon, and so on. Svetlana wants Mike to keep control, because he can best live out the life she was meant to leave. If she can’t live in peace, she wants him to.