Roy Clark...married to Dorothy Eva Manahan

Looking for info on my grandfather Roy Clark, born appx 1888/89.He pictures of him - very dark skinned, very handsome.Remember my mother telling me she had been told her background was possibly Indian/French/Irish.He married Dorothy Eva Manahan in Maryland.They were both orphans. They had six girls: Cecelia, Vera (both born in Michigan), and Mildred, Dorothy, Gloria and Elva; born in Wash DC.They moved from Michigan to Wash DC appx 1922. He fought in WWI in the Calvary. buried at Arlington Nat'l Cemetery.Died at Mt Alto Hosp, Wash DC (army hospital)from pancreatic cancer.Not sure but believe he had a sister, in Michigan who died in a fire.Left behind husband, child(ren).