Pretender

One who lays claim, or asserts a title (to something); a claimant.

The pretender (Eng. Hist.), the son or the grandson of James II., the heir of the royal family of Stuart, who laid claim to the throne of Great Britain, from which the house was excluded by law.

One who pretends, simulates, or feigns.

a claimant to the throne or to the office of ruler (usually without just title)