Alexander Vindman—the National Security Council’s top Ukraine expert who will testify before House impeachment investigators Tuesday—took his twin brother along to a meeting where he voiced his concerns about Donald Trump’s July telephone call with the Ukrainian president, The New York Times reports. In a profile of the latest star witness in the impeachment proceedings, the newspaper reports Vindman’s twin brother, Yevgeny, also works for the NSC and the two have offices across from one another in the West Wing of the White House. Yevgeny is a lieutenant colonel in the Army and serves on the NSC as a lawyer handling ethics issues. When Alexander decided to raise his concerns about Trump’s conduct, he turned to his twin and brought him along to a conversation with John Eisenberg, the top NSC lawyer. The twins were 3 years old when they fled Ukraine. Alexander Vindman will become the first sitting White House official to testify in the impeachment inquiry into Trump’s dealings with Ukraine.