There were three Venetian painters named Bellini. Jacopo (c. 1400-1470/1) was the father. The brothers to whom Ruskin is referring here are Gentile Bellini (c. 1429-1507) who is said to be Jacopo's elder son, and Giovanni Bellini (c. 1430 - 1516) who is said to be Jacopo's younger son.