Amnesia se jyada MPD makes sense and will be something different, but I highly doubt that CVs are that intelligent.
But, it sure is a nice theory, fits nice with Humeira's secret illness. Mental illnesses/issues are often not treated and hidden in a closet away from society's eyes - a very much Gafoor's thing.Now, I will make my thoughts run wild. What if, Shireen also has some or other form of mental illness (her dumbness is astonishing) and that is why Gafoor took her as his sister. Of course, he still hides such things from society, but he connected her with Humeira, and took her under his wings.