Kylie & ex-fiancée Joshua Sasse. They promised to marry if Australia legalized gay marriage but broke it off.

They vowed to marry once Australia legalized gay marriage.

https://www.independent.co.uk/news/people/kylie-minogue-husband-joshua-sasse-same-sex-marriage-australia-a7347721.html

They split in 2017; allegedly, he was unfaithful.

https://www.independent.ie/style/celebrity/celebrity-news/kylie-minogue-was-deluded-thinking-her-relationship-with-ex-fiance-joshua-sasse-needed-saving-36833176.html

https://www.hellomagazine.com/celebrities/2018040447498/joshua-sasse-crytlic-instagram-kylie-minogue-split-interview/

Still a better love story than Twilight.