Introducing a man,a woman said,"He is the only son of my mother's mother." How is the woman related to the man?

$A$ family consists of six members $P, Q, R, X, Y$ and $Z$. $Q$ is the son of $R$ but $R$ is not the mother of $Q$. $P$ and $R$ are a married couple. $Y$ is the brother of $R$. $X$ is the daughter of $P$. $Z$ is the brother of $P$.
Which is a pair of brothers?

$P$ is the brother of $Q$ and $R$. $S$ is $R$'s mother. $T$ is $P$'s father. Which of the following statements cannot be definitely true?

Pointing to a boy,Seema said,"He is the son of my grandfather's only child". How is the boy related to Seema?

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 $T$?

In a family,there are six members $A, B, C, D, E$ and $F$. $A$ and $B$ are a married couple,$A$ being the male member. $D$ is the only son of $C$,who is the brother of $A$. $E$ is the sister of $D$. $B$ is the daughter-in-law of $F$,whose husband has died.
How is $F$ related to $A$?