If you wanna know, go to the end of this writing and see the answer but it wont make sense if you just read that, it will make sense if you read all of this.
I gotta say, I've watched almost all alien series and i think I've figured it out that where is the xeno-morphs came from.
OK, so in the first movie alien, the star-ship Nostromo got a distress signal from an unknown alien vessel. The place they landed was on Lv426. A The team went to go investigate then they saw the eggs in the space jocky( Alien Ship), yep, we get it. xeno-morph got to them. You know what happens in alien okay?
Ripley escaped and was the survivor and went to cryo freeze. In the next movie called Aliens, which is the 2nd movie. Ripley was luckily found in a shuttle and yeah, she woke up at a hospital or something. She tells these people, idk who, but she tells them about the xeno-morphs on Lv426. And that's where the xeno-morphs where found. They didn't believe her because they said, there's nothing wrong with Lv426 and there hasn't been a problem about these creatures. There is a colony on Lv426 as they told her, she was in shock and she asked, '' how many families?''. The people said about 70 families. OK never mind about aliens, if you are reading this, you've probably watched the second movie ( Aliens ). A family got to a space jocky and yeah, a xeno-morph got to them. Yep a xeno-morph, a face-hugger from the same place from the first movie. They are on the same planet Lv426. So, you guys get it? Xeno-morphs came into Alien, to Aliens but where did they come from? Oh my friends, i think i know.
All the alien series( movies ) are in a timeline right? And Prometheus is a prequel to alien. Which means prometheus is first in the timeline
I'm pretty sure that there were no xeno-morphs, before the prometheus time. Which means that in prometheus. The Xeno-morphs species were created, and i think i was the only one who knows that made them. Engineers? NO. Lets get to it!!
As you the the android from prometheus sabotaged Dr Holloway's drink and he got infected with the black goo. He had an affair with Elizabeth before turning into an alien Zombie. That made her pregnant with an alien baby which was the first face-hugger! She went to take out the alien with a machine, idk how to describe it. It looked like an alien snake from the black goo. It is a hybrid, i think sort of a human and black goo. At the end of prometheus. The first face-hugger goes into the engineer and then the first Xeno-morphs species were created!! There you go!! All the deaths in alien series(movies) were all because of a curious android named David. If it weren't for his sabotage, none of this would of happen in the movies. But it did and the mother of the species (Xeno-morphs) is Elizabeth Shaw.
All this is based on my opinion and the alien movies I've watched, if you think it is wrong, do you have an answer why?
Elizabeth Shaw created the species known as Xeno-morphs shown in prometheus. There's only one problem, I haven't seen Alien Covenant and i don't know what a protomorph is. I don't know the origin of proto-morphs. Maybe they're different species.