ばか！バカ！　馬鹿ー月！

Tatsuya can't be Maya's child because in Volume 8 she got raped and was not able to have kids because of it. that is also the reason she did not get married.

Yeah but because the extent of her injuries was never disclosed some people she may have just lost to ability to carry children to term. Or maybe her eggs/ovaries were recovered from Dahan. There are a lot of theories about it.

the only way for Tatsuya and Miyuki to be testing as full siblings if Miya is Miyuki's mother and Maya is Tatsuya's mother (or vise-verse) would be if Shiba Tatsurou was there father and did the nasty with both Miya and Maya
and that would only be if Miya and Maya were Monozygotic twins like Kasumi and Izumi(Saegusa) but as Venom_is_an_ace said:

The central problem we seem to be running into is that we do not know exactly what Dahan did to Maya. Did they destroy her uterus so she can't have kids, but leave her eggs? Did they destroy her eggs? Did they collect her eggs? Did the Yotsuba get them after destroying Dahan? Until we know what went down we are at a point where nothing can be exactly pinned down.

Mahesvara wrote:The central problem we seem to be running into is that we do not know exactly what Dahan did to Maya. Did they destroy her uterus so she can't have kids, but leave her eggs? Did they destroy her eggs? Did they collect her eggs? Did the Yotsuba get them after destroying Dahan? Until we know what went down we are at a point where nothing can be exactly pinned down.

guys, you are forgetting about Minoru, who was created artificially, then It is possible to create Miyuki or Tatsuya by Yotsuba (If Kudo could, why not Yotsuba, or maybe Kudo was inspired by Yotsuba experiment, and created Minoru), also, there were few guessing about Miyuki in Volume 5 (something connecting to genetic makeup), so It is possible that Miyuki was created artificially

guys, you are forgetting about Minoru, who was created artificially, then It is possible to create Miyuki or Tatsuya by Yotsuba (If Kudo could, why not Yotsuba, or maybe Kudo was inspired by Yotsuba experiment, and created Minoru), also, there were few guessing about Miyuki in Volume 5 (something connecting to genetic makeup), so It is possible that Miyuki was created artificially

It's more likely Tatsuya was created that way. You have to remember that according Mitsugu the Yotsuba consider him their 'sin.' Something about his birth led them think like this.

They consider Tatsuya their sin because the had to change his brain with Miya's magic and he had became a failed artificial magician

kau_poria wrote:Well as per the Volume 16 preview Maya personally told Tatsuya that

Spoiler! :

"Miyuki is not your sister". So i just wonder what she actually means.
May be she is just toying with Tatsuya or may be she wants to see what he will do or she may be telling the truth. So now we will have to wait for Vol 16.

I would feel soooo vindicated if my theory proves to be true...

Just a quick theory that I came up with. What if Tatsuya was a child created by Dahan exiles who were able to smuggle out some of Maya's eggs? Of course, the Yotsuba would have none of that and eradicate the lab, but someone (Miya, Maya) decided to keep the baby. This would indeed make him the Yotsuba's shame, a reminder that they failed to protect Maya and her now infertility.

Lol, strangely, no posts here, considering all spoilers from v16 which come up on other forums