Both men, obviously, were President of the United States, and both men were assassinated. Both were talented orators, or at least speechmakers, with an ability to articulate abstract ideals in memorable phrases. The idealism that we associate with both men obscures the considerable political talents that they had. Both were pragmatic and canny bargainers who emerged from Congress. I am aware that an urban legend exists that points out a number of similarities between the lives and deaths of the two men, but those are almost all superficial, obviously coincidental, and in some iterations, factually wrong.
Are you refering to the ODD coincidences between the 2?
Kennedy's secretary was named Lincoln and Lincoln's secretary was named Kennedy. Both President's had a man named Johnson for a Vice President.
You can look up the rest, just google the appropriate terms.