Keegan DeWitt's birth name is Keegan Edward Arthur John DeWitt.
No, as far as what's known about both are concerned. Joyce DeWitt, who played the part of Janet Wood-Dawson on the long-running ABC-TV sitcom series "Three's Company", was born to Paul and Shirley DeWitt in Wheeling, WV, and raised in the Indianapolis area, in Speedway, IN. Rosemarie DeWitt was born in Flushing, Queens, New York, the daughter of Rosemarie Braddock and Kenny DeWitt. She is a granddaughter of boxer James J. Braddock,[4]and played the role of neighbor "Sara Wilson" in the movie Cinderella Man, which depicted James J. Braddock's life." ~ Wikipedia
Nope, sorry, they're not related in any significant way at all.
Steven Dale Green was born in 1985.
George Green - songwriter - was born in 1952.
Why is it
Matt DeWitt was born in 1977.
DeWitt Godfrey was born in 1960.
DeWitt Menyard was born in 1944.
George DeWitt was born in 1922.
Helen DeWitt was born in 1957.
David DeWitt was born in 1948.
Bill DeWitt was born in 1902.
Sam DeWitt was born in 1891.
Doug DeWitt was born in 1961.
Charles DeWitt was born in 1727.
Patrick deWitt was born in 1975.