MATHILDE de Louvain ([992/1000]-). The Genealogica comitum Buloniensium records that "Henricum seniorem de Bursella [=filius Ermengardis]" was father of "Lambertum comitem et Henricum fratrem eius et Mathildem sororem eorum", specifying that Mathilde married "comes Eustachius de Bolonia"[50], but this appears to be a confused representation of the situation. The primary source which confirms that Mathilde was the daughter of Comte Lambert [I] has not yet been identified but this is compatible with the chronology. Her birth date range estimated from the estimated date of her parents' marriage and the likely birth date of her eldest son in [1015/20]. This shows that it is chronologically impossible for Mathilde's father to have been the son of Ermengardis of Lower Lotharingia. m EUSTACHE Comte [de Boulogne], son of BAUDOUIN Comte [de Boulogne] & his wife Adelais of Holland (-[1049]). He succeeded in 1042 as Comte de Boulogne.
http://fmg.ac/Projects/MedLands/BRABANT,%20LOUVAIN.htm#MathildeLouvainMEustacheIBoulogne