"The four engine aircraft departed Douala Airport at 1416LT bound for Lagos. While climbing to an altitude of 6,500 feet, the airplane struck the slope of Mt Cameroon located 63 km northwest of Douala Airport. The wreckage was located few hours later 800 meters below the summit. Two passengers were seriously injured while 53 other occupants were killed. Three days after the crash, on May 6, one of the survivor died from his injuries and on May 9, the second survivor died as well. "
From
https://www.baaa-acro.com/country/cameroon?page=2 (need to scroll down a bit)
I suspect this is not the one your relative was involved in, as the wreck was found quite quickly. But it may be that they did not recover the bodies.
Thing is, the databases that are supposed to list all air accidents - commercial and military - don't mention any other incident in Africa in the time window between late '62 and Jul '63.
So... Maybe?