(Bloomberg) -- A New York real estate family that once did business with President Donald Trump is now trading fresh allegations of theft and betrayal, filing a lawsuit that could dredge up more details about Trump’s onetime partners in an ill-fated Manhattan hotel project.

Alex Sapir, whose company teamed with Trump more than a decade ago, on Friday sued real estate executive Rotem Rosen, who is Sapir’s brother-in-law and former business partner. Sapir alleges that Rosen siphoned tens of millions from his real estate company after recruiting additional members of his own family into the operation, according to the suit filed in New York Supreme Court.

Sapir also claims that in 2017, Omer Rosen, then the Sapir Organization’s general counsel, stole more than 1,500 sensitive company documents while negotiating the exit of Rotem Rosen, his brother, from the company.

“This action seeks to hold the Rosens accountable for their many alleged misdeeds,” Sapir’s lawyers at Oved & Oved LLP said in an emailed statement. “Both Rotem and his brother Omer, who allegedly conspired with him, have repaid our client’s trust with betrayal and mistaken its kindness for weakness.”

“The complaint is frivolous and is filled with blatant lies as will be shown in due course,” said Sheron Korpus, a lawyer for Rosen at Kasowitz Benson Torres.

It’s the latest salvo in a yearslong feud that has revealed some of the inner workings of a Manhattan real estate family founded by Soviet emigre Tamir Sapir, who died in 2014. Sapir’s company partnered with Trump and another real estate firm, Bayrock Group, to build the Trump SoHo condo-hotel in lower Manhattan in the years before the financial crisis.

The project was marred by sluggish sales and a fraud lawsuit, and it brought broader international attention to the Sapir Organization during Trump’s run for the presidency. The project was renamed the Dominick in 2017.

Rosen’s entry into the Sapir family began in 2007, when he married Tamir Sapir’s daughter Zina at Trump’s Florida Mar-a-Lago resort. But things fell apart after a 2017 dispute: Zina Sapir filed for divorce last year and Rosen launched a $103 million suit against Tamir Sapir’s estate. Rosen, in his lawsuit, alleged that he was owed compensation for deals prior to his exit.

©2020 Bloomberg L.P.