Source: comicsalliance.com

6. Lincoln March

“Owlman” might not be the correct name for this character but it’s the one that gets unofficially used by fans.

Lincoln March was a mayoral candidate in Gotham City who also turned out to be a major figure behind the Court of Owls, and one of their most powerful Talon operatives. He also believed himself to be Thomas Wayne Jr., a long lost brother of Bruce Wayne’s. this was never confirmed, though, so he could have just been a crazy person and not the bat brother indeed.

March stayed undercover until he was required to break, at which point he attacked Batman and revealed his supposed true identity. Bruce refused to believe him and the two fought until a massive explosion made it seem that Lincoln had died.

He hadn’t, though, and resurfaced during Batman Eternal until the Court of Owls grew tired of his disobedience and kidnapped him.