Introducing a man,a woman said,"His wife is the only daughter of my father." How is that man related to the woman?

Read the following information carefully and answer the question given below. All the six members of a family $A, B, C, D, E,$ and $F$ are travelling together. $B$ is the son of $C$ but $C$ is not the mother of $B$. $A$ and $C$ are a married couple. $E$ is the brother of $C$. $D$ is the daughter of $A$. $F$ is the brother of $B$. How is $E$ related to $D$?

$A$ 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. Who is the sister of $T$?

Pointing to a man in a photograph,a woman said,"His brother's father is the only son of my grandfather." How is the woman related to the man in the photograph?

$A$ man pointing to a photograph says,"The lady in the photograph is my nephew's maternal grandmother." How is the lady in the photograph related to the man's sister who has no other sister?

Arun said,'This girl is the wife of the grandson of my mother'. Who is Arun to the girl?