$A$ is the son of $B$; $C$,$B$'s sister,has a son $D$ and a daughter $E$; $F$ is the maternal uncle of $D$. How many nephews does $F$ have?

$A$ family consists of six members $P, Q, R, S, T,$ and $U$. There are two married couples. $Q$ is a doctor and the father of $T$. $U$ is the grandfather of $R$ and is a contractor. $S$ is the grandmother of $T$ and is a housewife. There is one doctor,one contractor,one nurse,one housewife,and two students in the family. Which of the following are two married couples?

Pointing to a lady,a man said,'The son of her only brother is the brother of my wife'. How is the lady related to the man?

$A$ is $B$'s sister. $C$ is $B$'s mother. $D$ is $C$'s father. $E$ is $D$'s mother. Then,how is $A$ related to $D$?

Pointing to a photograph,Nikita said,'She is the only granddaughter of my grandmother's daughter'. How is the girl in the photograph related to Nikita?

There are six persons $A, B, C, D, E$ and $F$. $C$ is the sister of $F$. $B$ is the brother of $E$'s husband. $D$ is the father of $A$ and grandfather of $F$. There are two fathers,three brothers and a mother in the group. How many male members are there in the group?