
Theory
He is similar to an omega from omegaverse comics (there are many knockoff versions) and possibly they're placing this as him being THE or one of the first of his kind. In the beginning the characters (himself included) stated how he is a freak or monster so your thoughts on it being omegaverse could be correct.

Since the genre doesn’t say “Fantasy” or “Supernatural”, I second the above person’s opinion too: Ci Nian is most likely biologically intersex who was raised as male. If I remember right, most intersex people are infertile but some can bear children. So, maybe he’s like that? It might also have something to do with the pill he was forced to take shortly before he blacked out during his grandfather’s death or, both being intersex and taking the pill could be responsible. I hope this helped!

Yeah (⌒▽⌒) this is the first time I’ve seen so much confusion about a character’s identity in any work..mostly in BL (specifically its fantasy versions) the characters’ biological/sexual stuffs are disclosed before anything else.. The confusion would probably be quite annoying but everything else is pretty top-notch so I think the revelation will be positively significant to the plot..I’m personally leaning towards the intersex theory because representation but I’ve never seen variations of omegaverse aside from Harami Bara and that one pregman thingy so it’d be cool if its some omegaverse version, too( ̄∇ ̄")

I thought about that at first but then it would have been easier to be found out by now as they have been going at it with each other. The first time he was drunk but then after he realized he was pregnant went into hiding to give birth but the physical difference would have likely been noticed. Also isn't the first time tags have been inaccurate.
am i the only one who’s still fcking confusedt??? like how did ci nian fucking gave birth, is this an omegaverse or what?? and they havent said a single thing abt the alpha beta & omega thingy? so idk and why does wo wo call him his dad if he’s the one who gave birth which means hes the mom— im so fucking confusedt im literally squeezing my brain at this point