In his bio it says that he's Rose Rome's great-great-great-uncle, or the brother of her great-great grandfather, but since they don't appear on each other's family tree, it is uncertain. The creators most likely did not want to create several ancestors of Rose and just stated this for storytelling purposes.
Like every other deceased Sim in Barnacle Bay, he has a pale green skin and gray hair. It is possible his name is a play on the phrase, "When in Rome". Despite his bio stating that he was a guitar player, he does not have the Virtuoso trait, nor any guitar skill. His biography also suggests he was so healthy he lived to a very old age.