Viktor and Amalija Knavs, Melania Trump's Slovenian-born parents, took the oath of citizenship in NY on Thursday, their lawyer confirmed, BBC reported.
Viktor and Amalija Knavs took their oaths in NY, the Associated Press reports.
"It stands for a bedrock of our immigration process when it comes to family reunification", he added to The Times.
President Trump has frequently slammed the process under which legal U.S. residents can sponsor the admission of family members and other people who are not close relatives. Her husband, Donald Trump, has proposed ending most family-based immigration, which he refers to as "chain migration".
The first lady was born in Slovenia, then part of Yugoslavia, in 1970.
The Federal Building also houses immigration court and the local offices of the Department of Homeland Security, and its subsidiary, Immigration and Customs Enforcement.
Their ceremony was private for "security reasons", attorney Michael Wildes said.
Trump hasn't commented or tweeted about his in-laws' newfound citizenship.
Melania Trump became a USA citizen in 2006 after marrying Trump the year before.
While the President never mentions Saipov, who obtained his green card through the equally maligned diversity lottery, he has been known to detail the attack.
The Knavses' citizenship ceremony was kept hush-hush at the Jacob K. Javits Federal Building.
Wildes told ABC News on Thursday that the Knavses had engaged in "a wonderful journey like most have - millions have - in getting citizenship and waiting the requisite period of time".
The Knavses raised Melania in the rural industrial town of Sevnica while Slovenia was under the Communist rule. That type of family visa is exactly one of the categories that Trump and his allies have tried to repeal, saying they are harmful to the US.
She settled in NY in 1996 and met Trump two years later. Curious about the cameras, bystanders wandered over.
Mr Knavs is 74, two years older than President Donald Trump.
He went on: "It seems like we now have two immigration systems".