Ulrich I. von Ostfriesland, Graf von Ostfriesland, was born 1408 in Norden, Lower Saxony, Germany to Enno Edzardisna (c1380-c1450) and Gela Syardsna von Manslagt (-aft1429) and died 27 September 1466 Emden, Lower Saxony, Germany of unspecified causes. He married Foelke von Esens (-1452) . He married Theda Ukena von Oldersum (c1434-1494) 1453 JL .
He was the first count of East Frisia (1464). He adopted the surname of "Cirksena" (Syardsna, Sydzena) as heir to his mother's family.
|Offspring of Ulrich I. von Ostfriesland and Theda Ukena von Oldersum (c1434-1494)|
|Hebe von Ostfriesland (1457-c1477)|
|Gela von Ostfriesland (1458-1497)|
|Enno I. von Ostfriesland (1460-1491)|
|Edzard I. von Ostfriesland (1462-1528)||15 February 1462 Greetsiel, Lower Saxony, Germany||15 February 1528 Emden, Lower Saxony, Germany||Elisabeth von Rietberg (c1475-1512)|
|Uko von Ostfriesland (1463-1507)|
|Almuth von Ostfriesland (1465-c1522)|