Orangejello and Lemonjello, spelled that way, is an urban legend.
The "kernel of truth" behind the legend is that there have been a few men in the USA named Orangelo (spelled that way, not "Orangejello".) The earliest examples of these were born BEFORE Jell-O was invented, so the name can't be from the brand name, but is a blend of Orange and
Angelo. Orange was regularly used as a male name in the 19th century USA, probably because it was the surname of the Dutch royal family, not because of the fruit or the color.
Lemongello, spelled that way, is an Italian surname. There is a singer named
Peter Lemongello who was briefly famous across the USA about 35 years ago.
He still performs in
Branson, Missouri. The stories about Orangejello and Lemonjello started at about the time he was in the news. So probably someone who had heard of a man named Orangelo put this together with the Italian surname Lemongello and invented the urban legend about the non-existent twins.