Complex sentence: The earliest known member of the house, Esiko, Count of Ballenstedt, first appears in a document of 1036, and is assumed to have been a grandson (through his mother) of Odo I, Margrave of the Saxon Ostmark.
Split into simpler sentences: The earliest known member of the house, Esiko, Count of Ballenstedt, first appears in a document of 1036. He is assumed to have been a grandson (through his mother) of Odo I, Margrave of the Saxon Ostmark.