second fiddle to (someone)

A role, position, or part that is less important than or subordinate to that of someone else. I'm really sick of playing second fiddle to this ignoramus—I'm the one who deserves to be the star of the show! He had aspirations of moving ahead in the company, but by now it seems like he's destined to remain second fiddle. Tom often felt like he was second fiddle to his older sister because of all her achievements in sports and academics.