Explanation:

- L and M are a married couple. L is the father with two children of different genders, and M is his wife.

- G is the son-in-law of M, which means G is married to M’s daughter, P.

- Therefore, P is L's and M's daughter and the sister of one of L's children.

- R is the sister of Q and not married, which means they are siblings.

- Q is the maternal granddaughter of L, thus confirming P is Q's mother.

- Q is married to K.

We need to find J's relation to Q:

- Since P is Q's mother and L's daughter, P has a brother (a sibling other than R since genders are different), and that sibling is J.

- Therefore, J is Q’s maternal uncle.

The correct answer is: Option 3, Maternal Uncle.