A lawyer for Viktor and Amalija Knavs said that the first lady's Slovenian mom and dad took the citizenship oath on Thursday in Manhattan.
The couple, who had been living in the USA on green cards sponsored by Mrs Trump, took the citizenship oath in NY.
Trump's in-laws Viktor and Amalija Knavs took the oath of citizenship, their immigration lawyer Michael Wildes confirmed to AFP.
Asked about President Trump's heavy rebuke of family-based migration, Wildes said: "I can't comment on the President's politics when it comes to my clients but I have stood up against the President's immigration policies personally".
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I am so proud about them because they were very focused on trying to arrive in a very good condition. ... "Maybe players stay to to the level, give time, different - maybe don't to risks, they more preparation, the or of injuries different".
The first lady was born in Slovenia, then part of Yugoslavia, in 1970.
Mr Knavs is 74, two years older than President Donald Trump. She became a United States citizen in 2006. That preferential program, popularly known as the "Einstein visa", is intended for immigrants with "extraordinary ability, [who] are an outstanding professor or researcher, or are a multinational executive or manager", according to the U.S. Customs and Immigration Services. They frequently travel with the Trumps and split their time between New York, Palm Beach, Florida, and Washington, where they stay in the White House. Melania was not present for the ceremony as she was in Bedminster, New Jersey, at the Trump National Golf Club, where the President is now staying.
However it's unclear whether their green cards were granted by a process the President has sought to end. It's unclear when the Knavses obtained permanent residency in the US, the Times reports, but Wildes said they met the five year requirement. They had no comment at the time, but the building where they were spotted holds offices where federal immigration officials process applications for citizenship.
The report quoted their lawyer as saying that the couple had met the five-year requirement, but added, "I can't give further comment".
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The Knavses' citizenship ceremony was kept hush-hush at the Jacob K. Javits Federal Building.
"They have travelled a wonderful journey like many have, like millions have", said lawyer Michael Wildes.
The Knavses, both in their 70s, raised Melania Trump in Sevnica, a Slovenian town of around 4,500 people.
Viktor and Amalija Knavs listen as their attorney makes a statement in New York, Thursday, Aug. 9, 2018.
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