A Republican senator is calling for an investigation into the business dealings of Donald Trump Jr. and Hunter Biden following the revelation that a Russian oligarch paid for Trump Jr.’s post-wedding festivities in the Caribbean earlier this year. Sen. John Curtis, R-Utah, sent a letter Monday to the leaders of the Senate Judiciary Committee requesting that the panel subpoena the president’s eldest son as well as former President Joe Biden’s son for testimony. NBC News’ Ryan Nobles reports