"Otto I, Count of Waldeck (c.1262 - 11 November 1305) was the count of Waldeck from 1275/76 until his murder in November 1305.
Otto was the youngest son of Henry III of Waldeck and Matilda of Cuyk-Arnsberg, a daughter of Count Gottfried III of Arnsberg and heiress of Wewelsburg. Henry III died in 1267, a few years before his father, Count Adolf I of Waldeck, and therefore the inheritance of Waldeck went from Adolf I to his grandsons. Henry III's eldest son Adolf II of Waldeck served as regent of the County of Waldeck upon his grandfather's death in 1270. However, at the time of Henry III's death, his three sons with their mother Matilda decided that the County of Waldeck should descend to whomever of the three sons were to marry the then underage Sophia, daughter of Henry I, Landgrave of Hesse. Ultimately, it was Henry III's youngest son Otto who married Sophia of Hesse in 1275/76. Upon the marriage of Otto and Sophia, Adolf II abdicated rule of the County of Waldeck in favor of his brother Otto and entered the clergy, later becoming Bishop of Liège in 1301. Henry III's second son, Gottfried, became Bishop of Minden in 1304. Their sister Adelheid married Simon I of Lippe in Detmold in 1276." - (en.wikipedia.org 28.05.2022)