Gu Yuzhi is a child whom the Gu Family patriarch rescued and adopted early on, and his birth registration indeed lists his blood type as AB.
However, he has been healthy since childhood, with no hospital stays or surgeries, and rarely went for physicals. Only when he was entering university did the school hospital discover a mistake: he wasn't AB; he was pure A.
He didn't think much of it and never bothered to amend the details on his birth certificate, nor did he mention this trivial matter to his family.
Yet, since Bao Gucheng managed to dig out Xi Zuzi's medical check-up records from childhood, it wouldn't be difficult for him to find Gu Yuzhi's school hospital records from back then.
But instead, Bao Gucheng publicly announced his blood type as the fake AB.
Men and women with AB and B blood type combined cannot have a child with O blood type.
Children born to parents with pure A and pure B blood types, however, might be O blood type.
