A couple was found dead in their Fayetteville home on Feb. 21, 1985. Officials said 24-year-old Kelly McDuffy and his wife 20-year-old Bobbie Michelle McDuffy suffered sharp force trauma to the upper body.
Investigators reopened the case in September 2007. Detectives said the investigation led them to Georgia, where Kelly McDuffy's brother was in jail for attempted murder in another case.
Forty-eight-year-old Sean Patrick McDuffy has been serving time in Hardwick, Georgia, after trying to decapitate his girlfriend.
Sean McDuffy lived with the couple at the time of their deaths.
Sean McDuffy pled guilty to two counts of first degree murder in the deaths of his brother and sister-in-law on Monday. He was sentenced to 20 years in prison for each count of murder.