Washington - Vice President Joe Biden announced on Saturday that his son, Beau, has died of brain cancer. Beau Biden was 46."It is with broken hearts that Hallie, Hunter, Ashley, Jill and I announce the passing of our husband, brother and son, Beau, after he battled brain cancer with the same integrity, courage and strength he demonstrated every day of his life," the vice president said in a statement late on Saturday."The entire Biden family is saddened beyond words. We know that Beau's spirit will live on in all of us, especially through his brave wife, Hallie, and two remarkable children."Obama prays for BidenPresident Barack Obama said he and the first lady were grieving alongside the Biden family."Michelle and I humbly pray for the good Lord to watch over Beau Biden, and to protect and comfort his family here on Earth," Obama said.The younger Biden was a lawyer, member of the Delaware National Guard and former Delaware attorney general.He was hospitalised earlier this month at Walter Reed National Military Medical Center. The vice president's office had declined to say what he was being treated for.In 2010, Beau Biden suffered a mild stroke. Three years later, he underwent surgery at a Texas cancer centre 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.