The U.S. Army officer who has emerged as a key witness in the impeachment proceedings against President Trump is from a family of Jewish refugees who fled Ukraine in 1979 when it was under the yoke of the Soviet Union.

Harvard-educated Alexander Vindman and his twin brother Yevgeny left Ukraine when they were three. Both are now 44-year-old lieutenant colonels working in Trump's White House on the National Security Council. Alexander is Director for Ukraine and Yevgeny, a military lawyer, works on ethics issues.

Sauce:

https://www.washingtonexaminer.com/policy/defense-national-security/alexander-vindman-twin-brother-ukrainian-refugees-army-lieutenant-colonels-who-both-now-work-in-trump-white-house

BTW:

Yevgeny is a lawyer who works in the same office in the NSA that reviews for release for publication of possibly classified info of books written by Whitehouse personnel. (Like Bolton's Book)