Earnest Lee Hargon heard the three charges of capital murder read in Yazoo County, while about 100 miles to the southeast, teams of officers searched Pine Woods for any trace of Michael and Rebecca Hargon and their four-year-old son, James Patrick.
Earnest Lee Hargon is Michael Hargon's cousin.
Friends and family of the missing family, many visibly shaken, watched the brief court appearance. Hargon is being held without bond at an undisclosed location.
Warren Strain, spokesman for the Highway Patrol, said the bodies have not been found. Capital murder carries a maximum death sentence.
Lawmen were swarming over property in rural south Mississippi Monday looking for the bodies.
Hargon was arrested on Friday on unrelated drug charges at his home north of Taylorsville.
The new search area is near the Smith-Covington county line just off state Highway 37 near the Hot Coffee community.
District Attorney James Powell declined to say what Hargon said during questioning.