The phrase "ugly stepchild" is used to describe something or someone that is treated unfavorably or neglected compared to others. It suggests unfair treatment or being considered less important. Full definition
Exploring the full capabilities of acrylic paint — what she calls the «ugly stepchild of oil paint» — Moyer often works on the floor, pouring, rolling, stippling, mopping and handworking the paint, as well as adding sections of glitter. (scadmoa.org)
Once the ugly stepchild of Asian automakers, Hyundai has significantly increased in both safety ratings and reliability in recent years. (babybunching.com)
In 2008, gubernatorial races were the ugly stepchild of the election family. (voices.washingtonpost.com)