pretender

US /prɪˈten.dɚ/
UK /prɪˈten.dɚ/
1.

kẻ giả vờ

a person who states they have a right to the high position that someone else has, although other people disagree with this:

:
The rebel forces are led by the pretender to the throne (= the person who wants to replace the present king or queen).