Kristin Cavallari, 37, proudly shows off her shirtless boyfriend Mark Estes, 24, in gym selfie as they work up a sweat together - after admitting 13-year-age gap was a 'hang up'

Kristin Cavallari, 37, proudly shows off her shirtless boyfriend Mark Estes, 24, in gym selfie as they work up a sweat together - after admitting 13-year-age gap was a 'hang up'
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