Q's mother is sister of P and daughter of M who is brother of R. S is daughter of P and sister of T. How is M related to T ?

Q's mother is sister of P and daughter of M => P is the child of M.
S is daughter of P and sister of T, so P is parent of T too.
M ----> parent --------> P ------------>parent -------------> T
But given M is brother of R => M is male.

So, M is grandfather of T.