Question : How many sons does X have ?

Statements :
I. Q and U are brothers of T.
II. R is sister of P and U.
III. R and T are daughters of X.

Explanation:-

From I, II and III, we conclude that all P, Q, R, T and U are children of X. Of these, Q and U are male while R and T are female. But the sex of P cannot be determined.