In my story in progress, I have a hero that is pursuing a quest, but I also wanted to develop a romance between the main two antagonists. When I mean developing a romance, I mean like they meet each other the first time, slowly get closer, and become a couple. Is there a point in writing romance between the main antagonists if the hero is suppose to defeat them (even if they both are doomed to fail when the hero wins and they lose)? If so, how should the reader/viewer care about the two romantic antagonists if they work together to defeat the hero. I've seen two heroes fall in love with each other a lot, but rarely two antagonists in love. Since that is uncommon, is the reason behind that because readers would struggle feeling invested in them?