Template:Notability Nisien is a figure in Welsh mythology, the son of Penarddun and Euroswydd and twin brother of Efnysien.<ref>Template:Cite journal</ref> He appears in the Second Branch of the Mabinogi, which names Brân the Blessed, Branwen, and Manawydan as his half-siblings. Nisien, also Nissyen, was the opposite of his brother Efnisien in personality. He was tranquil and generous, while Efnisien was vindictive and destructive.