Well, why would he have to be. A jellyfish is odd to us but not an alien. Researchers find new life frequently enough that it seems obvious that there are still lots of species that have never been discovered, that may never be. That there are many that had come about and then gone extinct. There may also be other types of life that don’t fit the current definition, are not within the boundaries we have set, and so we don’t see them at all and we don’t know how to look for them.
He looks just like a man though. She brought him back to the subject. He does, he agreed. But not all of his kind do. They always resemble their mothers. The mother forms them. But the mother is human. So they’re half human. No. He shook his head with adamantium surety. Firstly the mother is not always human. She could be anything, but they pick the mother from whatever seems to be the dominant species at that time and place. His father saw humans as dominant. But his father wasn’t human. Secondly they are only in appearance like the mother. Her genes only provide the form so that she can grow the child inside her. Their species is not a fixed one, at least in body.