Big Brother and The Amazing Race alum Claire Rehfuss has addressed rumors Derek Xiao cheated on her when they were still together.
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Claire, 29, took to X on Sunday, February 1 to share a screenshot of a comment that read, "Claire BB23 liking two of my TikToks that exposed Derek BB23 of cheating on her with his coworker Olivia and dating a week after they broke up."
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The X user, who had originally posted the screenshot, captioned their post, "Derek from BB23 cheated on Claire. Whitney's karma," referring to how fellow Big Brother 23 alum Whitney Williams was angry at Derek after discovered he had betrayed her.
Claire insisted that X user is a "random f-cking account" that "has been harassing" the former couple since they wrapped filming Big Brother's 23rd season in 2021.
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"They've been racist, made up SA claims, threatened to kill my niece, harassed people I've followed etc," Claire vented.
Claire went on to confirm, "Derek didn't cheat."
She also asked fans not to "engage with this pathetic stalker" who is behind the rumors.
Claire and Derek announced their decision to split in September 2025 after four years of dating.
Derek and Claire, who met on Big Brother in Summer 2021 and began dating in October of that year, released a joint breakup statement via Instagram Stories at the time.
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"After 4 wonderful years together, Derek and I have decided to end our relationship," the pair wrote.
"Nothing dramatic happened, just the realization that we're different people who want different things. We still care deeply about each other, are grateful for the time we shared, and will remain friends."
The former couple continued, "Thank you for all the love and support, it truly means so much. We hope that by sharing we can be given the space and grace to move forward without any speculation or drama."
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After they called it quits on their relationship, Claire took a break from social media until she returned to Instagram in November 2025.
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Derek was billed as a 24-year-old start-up founder when CBS viewers first met him on Big Brother's 23rd season.
Derek, a Maryland native who lived in New York at the time of his Big Brother stint, was evicted from the Big Brother house over his close ally, Claire, on Day 51 of the game.
While Derek -- a fan-favorite who was awarded the most "BB Bucks" by viewers during his season -- didn't play the winning game he had hoped to, he didn't walk away from Big Brother totally empty-handed.
Derek memorably made a romantic connection with Claire -- an artificial intelligence engineer who was also a New York resident at the time -- in the Big Brother jury house, and the pair began dating shortly after their Big Brother season ended.
"Coming out of the Big Brother house has been overwhelming, but I'm so lucky to have had Queen Claire by my side making me smile and laugh everyday," Derek wrote on Instagram in late 2021. "I'm so excited to see what's next for us!"
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Less than a year later, Derek and Claire returned to CBS to compete on The Amazing Race's 34th season and won its $1 million prize.
After racing around the world, Derek and Claire gushed about how their relationship was stronger than ever, and they moved from New York to Los Angeles together in 2022.
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That same year, Derek also competed on the first season of CBS' The Challenge: USA reality competition.
And in December 2023, Derek served as the co-host of CBS' Big Brother Reindeer Games holiday competition.