Ooh, fascinating. This born of human parents notion is the first I have heard of it. So what do two elves produce? An elf? Or a human? Do you have this written up somewhere?
My initial thoughts on the matter can be found here; however, that doesn’t address the specific question.
I want my Averoigne campaign to be human-centric. D&D, as originally conceived was supposed to be that; however, according to my own experience, players seem to gravitate towards demi-humans anyway. Part of that is the various cultures and civilizations that these creatures have as part of their background.
Part of my thinking on demi-humans in Averoigne is to come up with an explanation why there aren’t any elven, dwarven or halfling civilizations or cultures — mom and dad are human. In addition, it also helps explain demi-human level limits — they have turned their back on their humanity in order to embrace the powers they get from being fey-touched. As a result, they can never reach their full potential.
Another reason that there is no demi-human civilizations or cultures is that any children they have are not guaranteed to be demi-human. The majority are human, and any fey-touched children may very will end-up being another type of demi-human.
A final reason for this lack of a culture or civilization is that a fair number of fey-touched abandon their humanity, not just embrace their demi-humanity. Once that happens, they become twisted (orcs, goblins, etc.) and often never turn back. At this point they cease to be human and become monsters. Any offspring at this point are not human, but more monsters.
A parting note: in an attempt to re-habilitate the idea of the half-elf, they are not half-human, half-elf offspring. Rather, they are fey-touched who are struggling to hold on to their humanity. They still have demi-human powers, but suffer penalties when using them.