They don’t come from intersex people. It can happen to anyones baby (but incredibly low chance). How they reproduce from there depends on how their sexual organs develop. I’m not really an expert on this but from what I can remember you can have people with wombs and overies but also born with a penis, you can have people born with balls which are actually overies, or overies which are actually testicles
etc. If you really want to know you can probably google it.
This also reminds me of the tribe in the Dominican Republic where kids are almost always born female, and only become boys at the age of 10/12. Basically they only grow penis’s and ball sacks once they hit puberty, but before then they basically have girly bits:
Bonkers, but shows that life isn’t as simple as we’re all male or female and need to fit neatly into those two boxes. A ‘x’ definition should probably exist for those who are intersex at the very least. Once you realise that sex isn’t always as straight forward as male/female, you can start thinking about how gender is a social construct…but I think that’s going to be a bridge way too far for avftt.