One could make a good case that the murderer of Henri III of France was less influenced by the Catholic League than Oswald was by the Soviets. Neither of them was sponsored if by sponsored you mean paid to do it. (He formed the plan *before* going to the Catholic League, who encouraged it.)
Then his relative, Henri IV, was almost killed in 1593 and again in 1594 by people who were radicalized by politics just as Sirhan Sirhan was because of RFK's support of Israel. He eventually was killed in 1610.
While the length between the deaths by assassination is great, if you go by near assassinations, that 1589-1594 mark is only slightly greater than the length of time between JFK's and RFK's murders, and the 1593 one (which I edited in becasue I hadn't know n about it, since the person was turned in before attempting it) is actually less.
The only difference is that the Kennedys were killed by people influenced by different politics (Oswald had spent time in the Soviet Union). Henri III and Henri IV were killed by random individuals who had it in for them for the same political reasons.
Frankly, my main concern is that this isn't some homework assignment, because it seems like a close enough link that I can imagine a professor of history giving this question. perhaps it was mentioned in class but the OP didn't attend that day.
But, that's just a silly conspiracy theory, now, isn't it, OP? Just because it *could* be true...
