The former couple started dating in the fall of 2020 and by January 2021, they were Instagram-official.
Yvonne Strahovski had returned to work to film Handmaid's Tale in July 2019, having given birth to William in October 2018.
She was pictured running errands in Los Angeles while wearing a diamond ring on her left ring finger.
Cowell was also one of the show’s hosts alongside Sharon Osbourne, Louis Walsh, and Nicole Scherzinger.
She had suffered a miscarriage in 2015.
At least two other women have had made similar accusations.