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(CNN) —  

Housing and Urban Development Secretary Ben Carson will name the son of his close friend and business associate as deputy chief of staff, the department confirmed Wednesday.

Alfonso Costa Jr., 29, is expected to join the department in the coming weeks, a source familiar with the decision told CNN.

The arrival comes as one of Carson’s closest political aides, deputy chief of staff Deana Bass, leaves the department and shortly after a relative novice to housing policy, Andrew Hughes, was promoted to chief of staff.

“Alfonso Costa Jr. is a graduate of Yale, Oxford and Harvard Law,” HUD spokesman Raffi Williams said in a statement to CNN. “If his academic achievements are any indication of success, we are confident he will make significant contributions to the Department. The Secretary looks forward to having him serve as trusted and valued adviser.”

Calls to Costa’s phone number were not returned.

Costa’s father is a dentist-turned-real-estate-investor who Carson has described as “one of my closest, if not my very closest friend.” Carson and his wife were involved in a 2007 real estate deal with the senior Costa. Later that year, after the elder Costa was convicted for health care fraud, Carson wrote on his behalf to the federal judge sentencing him.

“I could literally trust him with all of my earthly possessions and rest assured that I would get all of them back with interest,” Carson wrote to the judge. “To sum it up, next to my wife of 32 years, there is no one on this planet that I trust more than Al Costa.”

A New York Times reporter earlier tweeted the Costa hiring.

Carson, a former renowned neurosurgeon, arrived at HUD with no prior government or housing experience, and has previously landed in hot water for blurring the lines between close personal relationships and department business.

The agency’s inspector general is currently investigating the role of Carson’s family in official HUD business as well as the purchase of a $31,000 dining set for the secretary’s office suite.

His son, Ben Carson Jr., held and coordinated official meetings, including organizing an official “listening tour” event for Carson in Baltimore last year. Carson Jr. is not a federal employee and has business dealings in Baltimore – raising questions about whether Carson Jr. and his building company benefited from his father’s government position.

Secretary Carson called the revelations, based on internal emails, an “attack by the media,” and wrote in a social media post that he “insisted that HUD operate in an open and ethical manner.” He also called for the agency’s inspector general to review the matter, and that review is underway.

The Carson family has a decades-long friendship and business relationship with the senior Costa, who works in real estate in Pennsylvania. In 2007, they and Costa purchased a Pittsburgh office building, according to property and business records, which ties the Carsons to holding companies incorporated at Costa’s house. Carson also listed the two companies on the financial disclosure form he submitted in 2017 ahead of his confirmation as housing secretary.

One of the Costas contributed $5,400 to Carson’s presidential campaign in 2015; publicly reported campaign finance records are not clear whether the contribution was from the father or the son.