Two sources (Krämer and Schmidt, and "Romantic Notions") state that he was Leonardo's adopted son, probably dating from 1490 when he went to him as an apprentice. More generally accepted is the assumption that they became lovers. Leonardo gave the young Caprotti the name Salaì (Little Devil, or Devil's Offspring), because of his almost intolerable behavior: continually lying, stealing and breaking things. In spite of this they were together until Leonardo's death in 1519, and Salaì inherited the master's vineyard at Milan.
Another protégé, the aristocrat Francesco Melzi, is also believed to have been adopted by Leonardo.