Never confirmed by Gunn. There is an Easter Egg scene where it shows all the different species Ego has been with and one of them looked like Mantis. Most of us don’t think so because of what happens to Ego’s children when they do meet their father.

Potentially. I mean it makes sense that he is. Why would he breed with a Mantis species, have a Mantis spices child, but also take Mantis as his servant? It just doesn't make sense. So I believe she is.

It is not confirmed

It is not confirmed yet but it is very likely to be true.

Thank you all☺️

Not comfirmed, but I don’t believe she is.

Idk

James Gunn actually tweeted a month back or so saying that they aren’t related but Peter does have a dead sister/brother of the same species as Mantis.

EDIT: Trying to find the tweet but only find ones that leave the scene open for interpretation. Still, I’m convinced I’ve seen this tweet explicitly stating that they aren’t related.

@Hickix, I believe you were right about Gunn addressing it. People ask him about Easter Eggs in his films all the time and he did address it when he got asked by someone. I think the other key is all of the bones buried underground were all his offsprings and so I don’t think Mantis would still be alive at this point.

It's a cool theory but not confirmed yet.