(Author's note: The name Arathorn sounds similar to Aragorn because according to the plot, the two of them are related. They share a common ancestor.)
(TL's note: I couldn't find any Arathorn like that in the story. There's Arathorn II, who's the fifteenth Chieftain of the Dúnedain and Aragorn's father; Angamaitë, an important figure amongst the Corsairs of Umbar; and the Captain of the Haven, who is a Black Númenórean and the ruler of the Umbar, but I couldn't find an Arathorn who's a Black Númenórean and the leader of the Corsairs of Umbar. So just treat him as someone the author came up with.)