Birth Name: Matthew Christensen Duffer
Place of Birth: Durham, North Carolina, U.S.
Date of Birth: February 15, 1984
Ethnicity: Danish (maternal grandfather), Irish, likely English
Matt Duffer is an American film and television writer, director, and producer. He works with his twin brother Ross Duffer. The two are known as the Duffer brothers. They are known for creating the series Stranger Things.
Matt is the son of Ann Marie (Christensen) and Allen Pace Duffer.
Matt’s maternal grandfather was Carl Ravn Christensen (the son of Nels/Niels Peter Christensen and Matte Marie Ravn). Carl was born in the U.S., to parents from Denmark.
Matt’s maternal grandmother likely is named Estelle O’Connell.
Source: Obituary of Matt’s maternal grandfather, Carl Ravn Christensen – http://www.legacy.com