where did the half-breeds come from?

we know at least one halfbreed made it to part 3, and he woulda been gettin plenty of poon and making babies by the time he croaked.. however they would now be quarter breeds. If the guy from two wasn't bringing all his kids to the barn then it renders those scenes in two pointless.It's poor continuity that's all

True, but you also gotta remember that these things are more animalistic and I doubt they care about the half sister thing. She was their only chance of survival or "completing their mission". Idk, that's part of the reason I don't like this one. Makes a lot of sense to try and save your dying species by nailing your half sister. They already had genetic deficiencies. Inbreeding would not help things.

I find that somewhat unlikely that there would only be one left. Mainly because there were three halfbreeds in #3 that we know of and I somehow doubt that kid had any offspring because he was sick as hell when he met with Abbott. My guess is that not all of Patrick's spawn were in their shells when Press and Laura showed up with the alien spray (some were probably not old enough) and they managed to slip away at some point. Maybe Patrick had a few of them in hiding just in case something went wrong.