Beau Biden died of brain cancer in May 2015.
From Newsweek:
Joe Biden incorrectly described himself as the father of a man who "lost his life in Iraq" at a speech in Colorado on Wednesday. Speaking near the town of Vail, Biden designated Camp Hale, a 436-square-mile site where the 10th Mountain Division were trained during World War II, as a national monument. Biden saluted the bravery of the 10th Mountain Division in battle in Italy, before claiming he lost a son in Iraq. The president said: "Just imagine, I mean it sincerely, I say this as a father of a man who won the Bronze Star, the conspicuous service medal, and lost his life in Iraq. Imagine the courage, the daring, and the genuine sacrifice—genuine sacrifice they all made."