Only one of them is immortal and the son of SKY FATHER. Second twin always dies before the first one.
They are connected to the Gemini constellation and horses.
Vedic: अश्विन् (Ashvins) Nasatya and Dasra
Mitanni: Nasatya twins
Latvian: Dieva deli
Old Prussian: Potrimpus and Autrimpus
Greek: Polydeuces Castor and Pollux
Roman: Gemini Dioscuri
English: Hengist and Horsa ("Stallion and Horse")
Slavic: Dido and Dida Ledo and Lada
Polish: Lel and Polel
Sarmatian: Lebus and Polebus
Norse: Orgelmir and Bergelmir (primordial giants)
Welsh: Brân Fendigaidd and Manawydan fab Llŷr
Atlantic Celts: Dioskouroi
According to Tacitus (ch. 43) the Alcis were a deity of the Naharvali.
Among these last is shown a grove of immemorial sanctity. A priest in female attire has the charge of it. But the deities are described in Roman language as Castor and Pollux. Such, indeed, are the attributes of the divinity, the name being Alcis. They have no images, or, indeed, any vestige of foreign superstition, but it is as brothers and as youths that the deities are worshipped. — Tacitus. Ch.43