A Secret Daughter, Perhaps?
Ego’s quest for total dominance took him to all places in the universe. We’re not exactly sure how suave the man is, but being a man of power, he might’ve had countless children during his travels. However, he supposedly killed all of his kids after realizing that they weren’t like him.
However, when he goes over his expansion plan with Star-Lord, there’s a notable figure that looks oddly similar to Mantis. This begs the question, is Mantis Ego’s daughter? After all, he treated her mother the same way he did Peter’s. That would mean that Mantic and Star-Lord are step-siblings or Step-Guardians in a sense.