US President-elect Donald Trump on Sunday said Lebanese American businessman Massad Boulos would serve as senior adviser on Arab and Middle Eastern affairs.

Trump made the announcement on Truth Social. Boulos, the father-in-law of Trump's daughter Tiffany, met repeatedly with Arab American and Muslim leaders during the election campaign.

It was the second time in recent days that Trump chose the father-in-law of one of his children to serve in his administration.

On Saturday, Trump said that he had picked his son-in-law Jared Kushner's father, real estate mogul Charles Kushner, to serve as US ambassador to France.

In recent months, Boulos campaigned for Trump to drum up Lebanese and Arab American support, even as the US-backed Israel's military campaign against Hezbollah in Lebanon.

Boulos has powerful roots in both countries.

His father and grandfather were both figures in Lebanese politics and his father-in-law was a key funder of the Free Patriotic Movement, a Christian party aligned with Hezbollah.

His son Michael and Tiffany Trump were married in an elaborate ceremony at Trump's Florida Mar-a-Lago Club in November 2022, after getting engaged in the White House Rose Garden during Trump's first term.

Boulos has been in touch with interlocutors across Lebanon's multipolar political world, three sources who spoke to him in recent months say, a rare feat in Lebanon, where decades-old rivalries between factions run deep.

Particularly notable is his ability to maintain relations with Hezbollah, they say. The Iranian-backed Shi'ite Muslim party has a large number of seats in Lebanon's parliament and ministers in the government.

Boulos is a friend of Sleiman Frangieh, a Christian ally of Hezbollah and its candidate for Lebanon's presidency. He is also in touch with the Lebanese Forces Party, a vehemently anti-Hezbollah Christian faction, the sources say, and has ties to independent lawmakers.

Aron Lund, fellow at the Century Foundation think tank, said Boulos was well placed to influence Trump's Middle East policy after playing a small but significant role in expanding Trump's appeal to Arab American and Muslim voters during the campaign.

"Boulos' Lebanese political past gives no real indication of a geostrategic or even national vision, but it demonstrates ambition and a set of political allies that will stand out in Trump's circle like a sore thumb," Lund wrote.