Kacey Musgraves' ex-husband is Ruston Kelly, a singer and songwriter born in Georgetown, South Carolina. The couple met in 2016 and got married in 2017 but announced their divorce in 2019, which was finalized in September 2020. Ruston Kelly has released multiple albums and EPs and has written songs for various artists. The pair initially connected through music and songwriting before their relationship took a romantic turn.
Source: https://www.comingsoon.net/guides/news/1894117-kacey-musgraves-ex-husband-ruston-kelly-job-relationship-history