The Celts were a big time tribe in Northern Europe and the British Isles who many people are descended from today. Like all these other folks of Indo-European descent, they also had a version of the Dioscuri, though not much is known about them. We get a mention of them in a book by a Roman dude named Diodorus Siculus in his book Library of History. Check it out:
"The Keltoi (Celts) who dwell along the ocean venerate the Dioskoroi (Dioscuri) above any of the gods, since they have a tradition handed down from ancient times that these gods appeared among them coming from the ocean."