Consider the following relationships among members of a family of six persons, P, Q, R, S, T and U:

1. The number of males equals the number of females.

2. U is the mother of P and T (both sons).

3. S is the mother of two children, one boy and one girl.

4. Q is the son of P.

5. There is only one married couple in the family at present.

Which one of the following inferences can be drawn from the above?