Odyssey, Book 11 and Pindar, Nemean 10 provide additional, complementary information concerning the Dioscuri. Both passages are available online from the Perseus Project.
The reference in Odyssey, Book 11, translation by A. T. Murray, is around line 300, section dealing with Odysseus' seeing Leda (Lede) in Hades. (Incidentally, it may be of interest that this chunk of the Murray translation in the Perseus Project opens with a reference to the story of Oedipus. We will consider the various Homeric references to Oedipus is more detail when we study Sophocles, Oedipus the King.)
A more detailed version of the story of Castor and Polydeuces is found in Pindar, Nemean 10, translation by Diane Arnson Svarlien and others, line 55 to end, viz., str. 4, ant. 4, epode 4, str. 5, ant. 5, epode 5. (The story of the Dioscuri begins about halfway through this link.)