$A$ girl introduced a boy as the son of the daughter of the father of her uncle. The boy is the girl's:

$A$ and $B$ are brothers. $C$ and $D$ are sisters. $A$'s son is $D$'s brother. How is $B$ related to $C$?

$A$ and $B$ both are children of $C$. If $C$ is the mother of $A$,$A$ is the son of $C$ but $B$ is not the daughter of $C$,how are $A$ and $B$ mutually related?

Following questions are based on the information provided below:
$A \times B$ means $A$ is mother of $B$.
$A - B$ means $A$ is brother of $B$.
$A + B$ means $A$ is sister of $B$.
$A \div B$ means $A$ is father of $B$.
Which of the following means $R$ is maternal uncle of $T$?

$A + B$ means $A$ is the son of $B$; $A - B$ means $A$ is the wife of $B$; $A \times B$ means $A$ is the brother of $B$; $A \div B$ means $A$ is the mother of $B$; and $A = B$ means $A$ is the sister of $B$.
What does $P = R + Q$ mean?

$A$ 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 the two married couples?