Love stealers

Lover Stealers, also known as Homewreckers, are villains who abduct lovers or love interests, usually the ones of those that they antagonize. It is often done to coerce the victim into marriage but also happens when villains take hostages.

A Lover Stealer can also be an individual who has "stolen" a protagonist's love interest and begun a relationship with them much to the chagrin of that Hero.