What are the posts in SSC CGL?

The answer to this one is that the two are three generations apart, P is the great-grandson of T. It is not as difficult as it seems because if you list them as names rather than letters, it no longer sounds like an algebraic problem. The individuals go in generational order. Note in the beginning that there are a brother and sister, therefore the older generation will bear the same relationship to each sibling.

B, great grandson. Automatically you can rule out granddaughter and grandmother because P is a brother to Q. This leaves two answers.

If you reason carefully, you'll see that R is the mother of P and Q. R is the daughter to S, S is the son of T, and S if the grandfather to P, making P the great grandson of T.