How is P related to J?
A . M is the brother of P and T is the sister of P
B. P's mother is married to J's husband, who has one son and two daughters

Using statement A: We cannot find the relation using this statement as J's name is not even mentioned in it.
Using statement B:
We can say that J is the mother of P but cannot decide whether P is the son or daughter of J.
Using both statements together: We find, P is the daughter of J.