The Annalista Saxo names "Heinricum Crassum comitem…Sifridum de Boumeneburh et Cononem comitem de Bichlinge et tres filias" as children of Otto von Northeim & his wife. The Annales Stadenses name (in order) "Heinricum Crassum…Cononem comitem de Bichilinc…Sifridum de Bomeneburgh" as the three sons of Otto, specifying that Heinrich "fuit lantgravius, patrem Rekinsem imperatoris" and that he was killed at Norden in Frisia.
Graf von Northeim. He founded Kloster Bursfeld, as shown by the charter dated 23 Jul 1144 under which "Henricus dux Saxonie" confirmed the privileges of Kloster Bursfeld, founded by "comes Henricus filius Ottonis ducis, proavus meus".
The Annalista Saxo records that he was installed as Markgraf in Friesland by Emperor Heinrich III in 1101 but was killed while attempting to subdue the territory. The Annales Corbeienses record that "Heinricus comes Pinguis" was killed in 1101. 1
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