Quentin Roosevelt (1897-1918)

Quentin Roosevelt was the youngest of six children of US President Theodore Roosevelt. His father became president when Quentin was three and he was quite a rambunctious child. He ran with a multi-racial group of the sons of government workers and officials dubbed "The White House Gang". These Little Rascals terrorized the White House by spitballing presidential portraits, snowballing the Secret Service, and carving a baseball diamond into the White House lawn. At one point, Quentin snuck a pony into the elevator and brought him to visit his brother Archie's bedroom.

Quentin was intelligent and mechanically gifted. He attended Harvard University, but with World War I raging in Europe, he did what many sons of the elite did, he became a fighter pilot. There was even a famed group of Yale flyers dubbed "The Millionaire's Unit". Quentin was a popular but reckless pilot, even by the standards of a profession where life was often cheap and short. On July 14, 1918, Quentin's Nieuport 28 was shot down over France. The Germans buried him under a makeshift cross. They tried to make his death a propaganda victory, but it backfired because his father was still quite popular in Germany.

Six months after the death of his son, President Roosevelt died. Lieutenant Quentin Roosevelt's body was later reburied in the World War II American Cemetery next to his brother Brigadier General Theodore Roosevelt, Jr., who died serving in WWII. Theodore Roosevelt Jr.'s son and Quentin Roosevelt's namesake, Quentin Roosevelt II, also died in a plane crash, near Hong Kong in 1948.

Ted Williams (1918-2002)

I don't think there'd be many who would dispute the fact that Ted Williams is one of the greatest baseball players of all time. Wikipedia sums it up:

Williams was a two-time American League Most Valuable Player (MVP) winner, led the league in batting six times, and won the Triple Crown twice. A nineteen-time All-Star, he had a career batting average of .344, with 521 home runs, and was inducted into the Baseball Hall of Fame in 1966.

Williams was the last player in Major League Baseball to bat over .400 in a single season (.406 in 1941). Williams holds the highest career batting average of anyone with 500 or more home runs. His career year was 1941, when he hit .406 with 37 HR, 120 RBI, and 135 runs scored. His .551 on base percentage set a record that stood for 61 years.

Williams' records would have been even higher had his baseball career not been interrupted by service in World War II and the Korean War as a fighter pilot. In training he broke even more records and in combat he was awarded the Air Medal. Later in life he became an avid sports fisherman, hosted a fishing television show, and was inducted into his second hall of fame, the IGFA Fishing Hall of Fame.

At the end of his life, Williams struggled with heart problems and had a pacemaker implanted. He died of a heart attack at 83 on July 5, 2002. His will stated that he wanted to have his ashes scattered in the Florida Keys. Instead, his son had Williams cryogenically frozen by the Alcor Life Extension Foundation. This prompted a lawsuit from Williams' eldest daughter, during which his son and youngest daughter produced an ink-stained napkin with Williams' signature attesting to his supposed change of mind. His son died of leukemia two years later and was also frozen by Alcor. A former Alcor executive claims that Alcor employees drilled holes in Williams' head to insert microphones so they could listen to the sound of his brain cracking while it froze. They then reportedly balanced it on an empty tuna can and tried to dislodge it from the can by whacking it repeatedly with a monkey wrench while bits of frozen head sprayed the room.