Mr. Epshteyn, who grew up in Moscow, has written that he came to the United States in 1993 at age 11.
He grew up in New Jersey. His mother Anna Shulkina is a real estate agent in Princeton at an office of Long & Foster. His father Aleksandr Epshteyn
works in New Providence, N.J., as a project manager in the wireless unit of Alcatel-Lucent, the French telecommunications company.
Before this year, Mr. Epshteyn was a relatively minor player in Republican politics. In 2008, he served briefly as a communications aide for the presidential campaign of Senator John McCain of Arizona. During the 2012 election, he appeared occasionally on television as a Republican analyst.
His ascent in Mr. Trump’s campaign is tied to his friendship with Eric Trump, the candidate’s second-oldest son. Both men attended Georgetown University and he was a guest at Mr. Trump’s 2014 wedding.
Mr. Epshteyn also met his wife at Georgetown, and the couple, married in 2009, recently had a child.
Mr. Epshteyn describes himself as a managing director of a boutique investment bank. But his business career has not always been smooth.
In 2009, he became vice president for legal affairs at a small financial firm, West America Securities, in which his wife’s uncle, Charles J. Newman, held a stake. By then, the company and its chief executive, Robert B. Kay, who was a longtime associate of Mr. Newman’s, had a history of run-ins with regulators.
As a result of an episode involving Mr. Kay, the Financial Industry Regulatory Authority, a Wall Street regulator, took the unusual step in 2013 of expelling West America, effectively shutting it down. Mr. Epshteyn and Mr. Newman were not accused of wrongdoing in the matter.
This summer, a Texas company filed a lawsuit against Mr. Epshteyn’s current investment firm, TGP Securities.
The company, Sigma Development Corp., alleged that Mr. Epshteyn and his partner had accepted an initial $100,000 payment to help find investors for a Disneyland-style theme park in Houston, and then failed to deliver on promises.
Donald Trump named Boris Epshteyn, a Republican political strategist who has appeared as a surrogate for the president-elect on TV, as special assistant to the president.
Epshteyn, who is in his mid-30s and is Jewish, would also serve as assistant communications director for surrogate operations, according to a transition team statement.
In 2014, he was charged with misdemeanor assault after being involved in a bar tussle. The charge was dropped after Epshteyn agreed to undergo anger management training and perform community service.