play second fiddle
Assume a subsidiary role to someone, as in Mary resented always playing second fiddle to her older sister. This term alludes to the part of second violin in an orchestra. Although many would argue it is as important as first violin, it is the idea of subordinacy that was transferred in the figurative term, so used since about 1800.
Dictionary.com presents 366 FAQs, incorporating some of the frequently asked questions from the past with newer queries.