Castor and Pollux are TWIN brothers in Greek mythology. They were the sons of Zeus and Leda, and were known as the Dioscuri. Castor was a skilled horseman and Pollux was an expert boxer. The two were inseparable and often referred to as 'the Twins'. In some versions of the myth, they were even granted immortality by Zeus. The term 'Castor, to Pollux' is used to refer to the two brothers, with Castor being the first mentioned.