Wait a minute, Miyuki have 2 girls. One of them is Yukino's "mother" and the other one is the woman on the photo in Yukino's room. Now i think that the woman in Yukino's room is her biological mom and is probably dead and her "mom" is actually her aunt, that took up Yukino after the death of her sister. That explain why Yukino doesn't look her family at all, they are not her parents and brother/sisters but her aunt/uncle and cousins Probably like Nobara, both Yukino's parents die in an accident and that could explain why she cry in the cemetry back then, she understand what kind of pain Nobara as gone throught with the lost of their parents.