Explanation:

- L is the grandson of W and son of P. This means P is L's parent, and W is P's parent.

- C is the niece of U, and U is unmarried, so U must be a sibling of one of C's parents.

- R is the mother-in-law of T, meaning R is the parent of T's spouse.

- T has two children, so T is married and likely has a spouse in the family.

- There are only two married couples, and since P is L's parent, P is likely married to T.

- P does not have a sister, so P is either an only child or has only brothers.

Based on this breakdown:

- Option 3: R and T

- R, as T's mother-in-law, makes T the spouse of R's child.