Q, the Doctor, is the father of T. S, the Housewife, is the grandmother of T and hence the mother of Q. Since there are only two married couples one being that of Q, the grandfather of R. i.e, U must be married to S. Thus, R and T will be both children of Q and these must be the students So, P, who remains, shall be the wife of Q and she alone can be the nurse. Thus, U must be the contractor 

P is the nurse. 

Q, the Doctor, is the father of T. S, the Housewife, is the grandmother of T and hence the mother of Q. Since there are only two married couples one being that of Q, the grandfather of R. i.e, U must be married to S. Thus, R and T will be both children of Q and these must be the students So, P, who remains, shall be the wife of Q and she alone can be the nurse. Thus, U must be the contractor 

Clearly, R and T are children of same parent, So. R will be the sister of T. 

Q, the Doctor, is the father of T. S, the Housewife, is the grandmother of T and hence the mother of Q. Since there are only two married couples one being that of Q, the grandfather of R. i.e. U must be married to S. Thus, R and T will be both children of Q and these must be the students So, P, who remains, shall be the wife of Q and she alone can be the nurse. Thus, U must be the contractor 

The husband of P will be Q. 

D is father of A and grandfather of F. So, A is father of F. 

Thus, D and A are the two fathers. C is the sister of F So, C is the daughter of A. 

Since there is only one mother, it is evident that E is the wife of A and hence the mother of C and F. 

So, B is brother of A There are three brothers. So, F is the brother of C. 

Clearly, B and A are brothers. F is the brother of C So, three brothers are A, B, F. 

D is father of A and grandfather of F. So, A is father of F. 

Thus, D and A are the two fathers. C is the sister of F So, C is the daughter of A. 

Since there is only one mother, it is evident that E is the wife of A and hence the mother of C and F. 

So, B is brother of A There are three brothers. So, F is the brother of C. 

A, the father. is male B, the brother, is male, C, the sister, is female D, the grand-father, is male, E, the mother, is female F, the brother, is male. 

So, there are four males.