Answer the questions based on the information given below. There are seven members R, S, T, U, V, W and Y in a family, which consists of only three generations. There are only two married couples in the family such that number of male members is more than female members. Only married couples have children. W is the son-in-law of S. V is the grandmother of Y. S has three children. U has two sisters. R is not the mother of Y. How is R related to the mother of U?