Read the following information carefully and answer the question below :
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 grandfather of R and is a contractor.
S is 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?