Who among the following person doesn’t form a group?

Answer the questions based on the information given below. There are   12 people M, N, O, P, Q, R, S, T, U, V, W and X   who stay on   6 floors   (numbered 1 to 6) of a building but not necessarily in the same order. There are   two flats on each of the six floors.   The   flats are numbered as 1 and 2   on each of the floors and are from   left to right.   Flat no. 1 of the floor no. 2 is exactly above the flat no. 1 of the floor no. 1 and so on. Q and T stay on the same floor above the floor on which O stays, but not immediately above. There are only three floors between T and V, both stay on flat no. 2. O stays just below W and both stays on flat no. 1. O does not stay on even numbered floor. N stays on immediately above P and both stays on the same flat number. P stays on even numbered floor. S stays on the topmost floor. Only three floors between S and M, both stays on a  different flat number. X stays below R, both stay in different flat number. There is more than one floor between X and R.