Some of the footage in this movie had been previously seen in MGM's 1950 smash-hit, "King Solomon's Mines." On location in Africa for that film, director Andrew Marton had shot vastly more footage than made it into the movie's final edit; the studio prudently held onto it and used it instead instead in various other movies with an African setting, including this one.
In the novels, Allan Quatermain did indeed have a son named Harry; however, he died prior to his father.