Examine the following relationships among members of a family of six persons - A, B, C, D, E and F.
1. The number of males equals that of females.
2. A and E are sons of F.
3. D is the mother of two, one boy and one girl.
4. B is the son of A.
5. There is one married couple in the family at present. Which one of the following inferences can be drawn from the above ?