Jared Kushner, a trusted White House advisor, held meetings with top Russian officials and investigators believe he has “significant information” that would aid the authorities.
Ivanka Trump’s husband held meetings in December with the Russian ambassador, Sergey Kislyak, and a banker from Moscow.
He is being investigated because of the extent and nature of his interactions with the Russians.
The controversy has engulfed President Trump’s administration since he fired FBI Director James Comey on May 10.
A lawyer for Mr Kushner said in a statement that her client would cooperate with the investigation to clear his name.
Jamie Gorelick, the lawyer, said: “Mr Kushner previously volunteered to share with Congress what he knows about these meetings.
“He will do the same if he is contacted in connection with any other inquiry.”
Former FBI director Robert S. Mueller is now leading the probe into possible coordination between the Kremlin and the Trump campaign.
Donald Trump said: “There is no collusion between, certainly myself and my campaign – but I can always speak for myself – and the Russians – zero.”
The Washington Post previously revealed someone close to President Trump could be called into hearings as swirling controversy threatens to derail the Republican firebrand’s political ambitions.
Republican senator Lindsey Graham claimed the US Justice Department probe into alleged ties between Russia and Mr Trump’s presidential campaign is “a criminal investigation”.
Investigators are also focusing on the sacked national security advisor Michael Flynn and former Trump campaign chairman Paul Manafort.
In a statement last week, White House press secretary Sean Spicer said: “As the President has stated before – a thorough investigation will confirm that there was no collusion between the campaign and any foreign entity.”