Complex sentence: Following his assassination, Kennedy was honored by the Canadian government by having a mountain, Mount Kennedy, named for him, which his brother, Robert Kennedy, climbed in 1965 to plant a banner of the arms at the summit.
Split into simpler sentences: Following his assassination, Kennedy was honored by the Canadian government which named Mount Kennedy for him. His brother, Robert Kennedy, climbed it in 1965 to plant a banner of the arms at the summit.