Kathy Hilton Husband: 'RHOBH' Mauricio Umanky Feuding After Business Deal Gone Wrong? [VIDEO]

Kyle Richards' husband, Mauricio Umansky, and her brother-in-law, Rick Hilton, the husband of Kathy, haven't gotten along for years, but why?

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According to a new report, the two men were involved in a business dispute years ago, and haven't been able to get their relationship back on track since.

"Rick and his team wouldn't make Mauricio a partner, even after years of working there and a lot of success. So he left," a source told E! News on Wednesday. "Now, Mauricio is not welcome at any Hilton events. It puts Kyle in a terrible position because she always has to choose between her husband and her older sister."

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"There are problems between Kyle and Mauricio and Kathy and Rick, and that is because Mauricio went behind Rick's back when he started his business," a second insider added. "Rick did everything for Mauricio to get him started, he gave him clients, he introduced him to people. And then when Mauricio set up his own company, he did it covertly and informed Rick via email. Mauricio was not made a partner as he was not being 100 percent above board and so there were trust issues.

"Finally, once Mauricio's new company was set up, Rick and Mauricio came to a gentleman's agreement that they would not go after each others' agents, but then Mauricio went back on that promise and tried to poach staff. It's a huge mess," the source continued.

For more, tune into The Real Housewives of Beverly Hills season six on Tuesdays at 9 p.m. on Bravo.