The Lordships of Esens, Stedesdorf and Wittmund were united in 1455 when Sibet Attena, a loyal vassal of the future Count of East Frisia, Ulrich I, married Onna of Stedesdorf; the heiress of the Lordship of Stedesdorf. The year before, Sibet Attena had captured the castle of Tanne Kankena in Wittmund. Finally, in 1454, Sibet Attena also received the Lordship of Esens as a fief from Ulrich I. This gave him control over the entire Harlingerland. Sibet Attena was a scion of the powerful Attena family, an East Frisian chieftain family who owned many properties in the north of the East Frisian peninsula. After his marriage to Onna of Stedesdorf in 1455 he called himself Lord of Esens, Stedesdorf and Wittmund.