The National Search Brigade for Disappeared Persons says Jose Jesus Jimenez Gaona was slain in the Gulf coast state of Veracruz.
The state prosecutor's office said yesterday that three gunmen pulled up to the victims' vehicle and opened fire with high-powered weapons.
The couple's daughter Jenny disappeared in 2011 in the Veracruz city of Poza Rica.
Rival cartels are engaged in turf battles, kidnappings and disappearances in Veracruz.
As in other parts of Mexico, inadequate police investigation in the state has led relatives to start search groups that in some cases have uncovered clandestine burial grounds.