The Kanawha County's sheriff's department confirmed the deaths of Shain Gandee, 21, and David Gandee, 48, but said the third person has not been positively identified.
There was no sign of foul play and autopsies on the men's remains are to be conducted by the West Virginia Office of the Chief Medical Examiner to determine how they died, the sheriff's department said Monday afternoon.
The disabled vehicle, which belonged to the Gandee family, was found in a muddy, wooded area along a worn path.
Shain Gandee and his uncle were last seen at Larry's Bar in Sissonville at about 3 a.m. Sunday and were heard saying they planned to go four-wheeling, the Charleston [W.V.] Gazette reported.
Family members searched for the men most of Sunday before calling 911 to report them missing, the newspaper said.
Shain Gandee was one of nine people featured in the MTV show "Buckwild" about rural young adults. It has been compared to the recently canceled MTV reality series "Jersey Shore."
"We are shocked and saddened by the terrible news about Shain Gandee, and those involved in this tragic incident," MTV said in a statement. "We are waiting for more information but at this time, our main concern is for the Gandee family and their friends. Our thoughts and prayers are with them. Shain had a magnetic personality, with a passion for life that touched everyone he met and we will miss him dearly."