Based on this passage about Ted Kennedy, at the time of his death, who were the three longest-serving senators of all time?

Context: When Kennedy died in August 2009, he was the second-most senior member of the Senate and the third longest-serving senator of all time, behind Byrd and Strom Thurmond of South Carolina. Later that same year, he was passed by Daniel Inouye of Hawaii. Kennedy therefore held the record as the longest-serving Democratic member of Congress to solely serve as a senator until October 2021, when he was surpassed by fellow Democrat Patrick Leahy of Vermont.

Answer: Based on this passage, Robert Byrd, Strom Thurmond and Kennedy were the three longest-serving senators of all time.