A is the father of X; B is the mother of Y. The sister of X and Z is Y. which of the following statements cannot be definitely true?
B is the mother of Z
X is the sister of Z
Y is the son of A
B is the son of A
B is the wife of A
X, Y and Z are siblings and Y is the sister of both X and Z. So, we cannot say that Y is the son of A.