She knows, but you're mistaken about her and Nii-san. She was never part of the Matou family; I was born into the Tohsaka family, then adopted by the Matous later. [Even if that seems like a lifetime ago now. She was around five-years-old when she was adopted, but she hardly remembered anything about her life in the Tohsaka family anymore. What she did remember only made her more bitter about her situation.

At some point in a different route and thus alternate universe maybe!! But at that, Sakura simply nods. She knows more than anyone how accepting he can be! HF wouldn't have happened without it!!]