Some (at least one) died of natural causes.
Also, Reagan didn't die. Doesn't that kind of break the curse?
I was always fascinated by the Lincoln/Kennedy parallels:
Kennedy had an aide named Lincoln; Lincoln had an aide named Kennedy.
Kennedy's assassin shot him from a warehouse and fled to a theater; Lincoln's shot him in a theater and fled to a warehouse (OK, a barn, close enough
)
I'm pretty sure that there were several others I can't remember.