Simplify the following text for a Grade 7 native English-speaking person.
Original: Robert Francis `` Bobby '' Kennedy ( November 20 , 1925 â `` June 6 , 1968 ) , also referred to by his initials RFK , was an American politician , a Democratic senator from New York , and a noted civil rights activist . An icon of modern American liberalism and member of the Kennedy family , he was a younger brother of President John F. Kennedy and acted as one of his advisors during his presidency .
Simplified: Robert Francis `` Bobby '' Kennedy ( November 20 , 1925 â `` June 6 , 1968 ) , also called RFK , was the brother of former U.S. President John F. Kennedy .