Lincoln's secretary's name was Kennedy and advised him not to go to the theatre where he was gunned down; Kennedy's secretary, whose name was Lincoln, advised him not to go to Dallas.
Lincoln's assassin, John Wilkes Booth, was born in 1839; Kennedy's assassin, Lee Harvey Oswald, was born in 1939.
Both presidents were succeeded by a man named Johnson. Andrew Johnson, who succeeded Lincoln, was born in 1806; Lyndon Johnson was born in 1906.
Both presidents were killed on a Friday, from behind and in the presence of their wives.