$R$ is the daughter of $Q$. $M$ is the sister of $B$,who is the son of $Q$. How is $M$ related to $R$?

Pointing to a photograph,a woman says,"This man's son's sister is my mother-in-law." How is the woman's husband related to the man in the photograph?

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

Pointing to the lady in the photograph,Mrinalini said,"Her son's father is the only son-in-law of my mother". How is Mrinalini related to the lady?

$A$ 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 $P$.
Who is the brother-in-law of $R$?

$A$ 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 is $E$ related to $F$?