For more than a decade, Oren Alexander was one of the biggest names in ultraluxury real estate in Miami and New York City. He helped to broker the record-setting 2019 purchase of a penthouse at 220 Central Park South, a deal closed for nearly $240 million.

The real estate empire that he helped to build in the sky in multimillion-dollar perches of glass and steel in both cities is now crumbling under mounting allegations of violent sexual assault.

Mr. Alexander, 36, was accused in two separate lawsuits filed earlier this year of sexually assaulting two women more than a decade ago. Oren’s identical twin brother, Alon, an executive in a private security firm, is also named as a defendant in both complaints.

The twins are accused of jointly sexually assaulting two women in separate incidents — one woman says she was assaulted at a party mansion in the Hamptons and the other says she was drugged and then assaulted in Manhattan.

On Monday, Isabelle Kirshner, a lawyer for Oren and Alon Alexander, defended the brothers and described the complaints as money grabs in a statement to The New York Times. “It is disappointing [but not surprising] that plaintiffs’ counsel is resorting to their same generic playbook — file similarly fantastical boilerplate claims against supposedly deep-pocketed individuals without regard to the specific facts or truth,” she wrote in the statement. “In fact, our preliminary investigation of the claims has uncovered clear and irrefutable evidence that vindicates the Alexanders, which we look forward to presenting in court.”

Oren Alexander, with his older brother Tal Alexander, made a name for himself in big-money real estate, including with the record-setting penthouse. They co-founded Official, a brokerage that caters to ultrawealthy clients.