Matthew Gray and Gunnar Eric Nelson are the twin sons of the late singer Rick Nelson and Kristin Harmon Nelson. Their paternal grandparents are TV legends Ozzie and Harriet Nelson, and their maternal grandparents are football great Tom Harmon and actress Elyse Knox. Actor Mark Harmon is their uncle. They have an older sister, Tracy, an actress, and a younger brother, Sam, also an aspiring musician.