Question

My sister is my mother's daughfer

Answer 1

моя сестра - дочь моей матери

Answer 2

If I understand correctly, you're saying that your sister is your mother's daughter. That is a common relationship within a family. In a traditional family structure, a mother typically has biological or adoptive children, and your sister would be one of them. It's normal for siblings to share the same mother, as they are children born to the same parent or parents. Is there anything specific you would like to know or discuss about this?