Note: AR has Herbert III de Vermandois as her 2nd husband, but the noted French genealogist Settipani has Herbert as her 1st husband and Milo IV as her 2nd. The sourced dates seem to work better following AR (which is why I am leaving them alone); however, if Settipani is correct (and he is an expert), then Herbert III would have died before 992 (Settipani has Ermengarde's son by Milo, Renaud b. abt 993), and Herbert & Ermengarde's son Otto would have been born before 992/3 instead of about 1000.
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This is an excerpt from a post to SGM (full post is in notes under Ermengarde de Tonnerre), 5 Dec 1998, by Settipani, the noted French genealogist:
The Ascendancy of Ermengarde of Tonnerre : Part II
The family of Ermengardis (no 5), widow of Herbert, not the reverse, is not « Bar-sur-Seine » (one misunderstanding hypothesis of E. Petit: such a dynasty does not exist at this time). She was, I think, the daughter of Alberic II of Macon and his second wife.
Title: Newsgroup: soc.genealogy.medieval, at groups - google.com Page: Ed Mann, 15 Jun 1998 Text: following Stuart's "Royalty for Commoners" (according to Settipani, a mistake)
Title: Ancestral Roots of Certain American Colonists, 7th Edition, by Frederick Lewis Weis, additions by Walter Lee Shippard Jr., 1999 Page: 50-20 Text: no date, 2nd husb ,Ermengarde of Bar (according to Settipani, a mistake)
Title: Newsgroup: soc.genealogy.medieval, at groups - google.com Page: Settipani, 5 Dec 1998 Text: 1st husband
Ermengarde de Macon 
