If any sexual relations happen between the two, that is bound to come up between the two of them
Nope. Wrong. It might, but not every gal is into that. Even if they're in love, and if Jeph isn't portraying that, he's not the artist I know him to be.
Regarding anatomy, only Claire and Marten would have NTK - need to know. I see no reason why they should share that with voyeurs in the readership. I for one will not speculate on Marten's length, width, number and size of testes etc and if you wouldn't either, please grant the same respect for Claire's anatomy, whatever it might be.
I'm an educational activist, and a member of SAGE - Sex And Gender Education (Australia). So I do sometimes share details of my own anatomy, past and present, with medical students, and those with similar NTK. I don't share them here, even though I'm Intersex, so never had anything remotely resembling "normality" before surgical reconstruction. If anyone has a professional interest in the effects of CAH and 3BHSD, there are medical pictures on the web, and you can PM me if you're credentialed.
I'm also not interested in your anatomy, come to think of it. Such details are private, personal, and often sensitive. Please do not share them.
Finally...the mods have made it clear that there is a banhammer, and it will be used if needed. And unless I miss my guess, it's in mid-swing now unless the topic closes.