The younger Biden was a lawyer, member of the Delaware National Guard and former Delaware attorney general. He was 46.
Beau Biden was hospitalized earlier this month at Walter Reed National Military Medical Center. At the time the vice-president's office declined to say why he was being treated.
Beau Biden suffered a mild stroke in 2010 and underwent surgery at a Texas cancer center in 2013 to remove what was described as a small lesion.
He announced last year that he would not seek a third term as attorney general and instead planned to run for governor in 2016.
(The Associated Press)