St. Sylvester was born of noble parentage at Osimo, in the Marches of Ancona. Owning to his rare merit, the Canons of the cathedral of Osimo admitted him to share their dignity. When present one day at the funeral of an illustious man, a relative of his, he was struck by the hideous appearance of the body of a man who had been so handsome, and exclaimed: "I am today what he was, and one day I shall be what he is."

He immediately gave up everything and retired into a desert where he devoted himself to penance and meditation. "Later, he built at Monte Fano" says the Roman breviary, "a church in honor of the holy father Benedict who advised him in a vision to found a religious order whose rule and habit he described to him. It was the Order of the Sylvestrines."

This branch of the Benedictine Order spread in a short time and already numbered twenty-five houses in Italy when its founder died in 1267, at the age of ninety.