The subject of this article has been mentioned only and never actually shown in a comic book or on-screen. Despite their lack of physical appearances, information about them might still be relevant or interesting or at least worthy of documentation. Anything known about them is to be considered second-hand information.
The first one we took in -- he was like you. A child of two worlds. The son of a man from land and a woman from the sea. He also felt like he didn't belong. Though, it's fair to say Arthur has gotten over that.