What I am saying is there was an ERB revival in publishing during the '60s and '70s, which both of us were a part. Greg "Tarzan" is the right age to have been similarly influenced.Despite the revival of interest during that period, some of ERB's published works never made it to mass market, they remained obscure. The Tarzan Twins novellas, "The Man-Eater," "The Resurrection of Jimber-Jaw," and some other material never made it to mass market during that period.
Only someone very influenced by ERB to research things would know of those obscurities, the Twins stories are not generally considered canonical by many though they came from ERB himself.
So, basically, the twins inclusion gave me reason to consider it had credence. On the other hand, of course, some idiot could easily have come up with it independantly, in which case I do not care to consider why.