Since Harsh has no brother or sister, so he is his father's only son. Now, wife of my father's son ? my wife. 

So, Harsh's wife is the man's mother or the man is Harsh's son. 

E is mamed to A or D. But B is marned to D. Thus, E is married to A. 

Thus, A, B, C, D, E are the four adults and C, F, G are the three children in the family. B and D have a child G. A and E have two children. They are C and F Now. only F and G are girls.

So, C is a boy. Thus, C is A's or E's son. 

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, for definite the males are Q, the father and U, the grandfather 

The man's brother's father means his father is the only son of woman's grandfather

=> grandfather to the man also

=> Woman and the man are brother and sisters.

Only son of woman's grandfather ? Woman's father.

Man's brother's father ? Man's father

So. the woman is man's sister.  

Radha ----> Radha's mother ------> Mother's mother => Radha's Grand-mother.

Radha's Grand-mother's daughter-in-law ------> Radha's Aunt -----> Radha's Aunt's daughter => Radha's sister-in-law.

Clearly, the brother of woman's mother is the same as the brother of the father of boy's maternal uncle. So, the woman's mother's brother is the boy's maternal uncle's father. Thus the woman's mother's brother's son is boy's maternal uncle, i.e woman's mother's  brother's daughter is boy's mother.

Daughter of grandmother ? Aunt: Aunt's only brother ? Father. 

The man said, "Her father is the only son of my father."

Then the woman's father and the man's is the same

=> The woman and the man are brother and sisters.

Hence, the man is the brother of the woman.