Don't forget JFK's older brother, Joseph Kennedy Jr., who was the one being groomed for power. He was killed in WWII flying a top secret mission called "Operation Aphrodite"
Look up "Operation Aphrodite"
Joe Sr was an Irish up-start who made a fortune smuggling booze from Canada and buying property for pennies-on-the-dollar. Because of Joe Sr's Irish Catholic Democratic support FDR appointed Joe as Ambassador to England. The Irish and the English aren't bosom buddies. Because of Joe's Hitler sympathies he was an embarrassment to FDR and resigned when FDR was re-elected in 1940. Joe was also anti-semitic.
Joe Jr's death was "suspicious"
Papa Joe made some serious enemies.