This is the fictional character, for the author, see Edgar Rice Burroughs.
Edgar Rice Burroughs was the young nephew of John Carter back on his homeworld of Earth. Burroughs inherited the wealth and estate of John Carter after he seemingly died, but what Burroughs didn't know was that John Carter's consciousness had returned to Mars.
Burroughs appears at the beginning of the second book The Gods of Mars. He made sure his uncle's last will to be burried in a mausoleum of his own design was carried out. Afterwards he learned about his uncle's true fate as John Carter visited him a few times and told him about his adventures, which Edgar began publishing in the form of books.
In the foreword of "A Princess of Mars" Burroughs mentions that he was 5 years old when John Carter left to serve in the confederate army during the American Civil War, which would place his date of birth somewhere between 1855 and 1860. This makes the fictional Burroughs at least 15 to 20 years older than his real life counterpart, who was born in 1875. The fictional Burroughs is also still alive in 1967. He seemed to have inherrited his longevity from his uncle John.