Otto is a purported Count of Loon and father of Count Giselbert, who would have been adult roughly around the years 980-1000. He appears in only one much later document that is considered unreliable, so his existence is doubted. The list ofthe counts of Loon is normally started with Giselbert. Since Leon Vanderkindere's seminal publications at the beginning of the twentieth century, scholars have tended to ignore the medieval report of Otto and accept Vanderkindere's proposal that Giselbert's father was Rudolf, the son of Count Nevelung. More recently, proposals have been made that Otto might have existed and been a son or nephew of Rudolf. None of these proposals have led to any consensus and can only be taken as speculative proposals. Jean Baerten, whose works in the 1960s are seen as an authority for this subject, doubted the existence of Otto at all. The only record of Otto, the third continuation of the chronicle or Gesta of the abbey of St Truiden tells of the installation of Baldrick II as Prince-Bishop of Liege, and that he was the brother of Count Giselbert of Loon, and the son of Count Otto of Loon and Liutgard of Namur. It says Liutgarde's mother Ermengarde was a countess of Namur, without naming how she became countess, and a daughter of a Duke Otto. It also claims she was an ancestor to Godfrey of Bouillion. Criticism of this source, written long after the facts, centres around the more detailed information it gives about Liutgard.
One reason this account is often rejected is that this description of the mother of Gislebert seems almost identical to that of the implied wife of Gislebert, found in the Vita Arnulfi Episcopi Suessioniensis I.3, MGH SS XV.2, . As pointed out by Baerten, Félix Rousseau, an historian of Namur, treated the two Lutgardes as if both could be correct records, even though, if they were both true, it would giveconsanguinity problems.
Another concern is that her grandfather "Duke Otto" is often interpreted as being the one mentioned in the passage, Otto, Duke of Lower Lorraine, who died too early for him to possibly be great grandfather of Bishop Balderic and Count Giselbert. Jongbloed, following Rousseau, believes this Duke Otto must be the one who died 944, Otto, Duke of Lorraine.
In summary, although there is a high chance of this being wrong, the Gestorum Abbatem Trudonensium Continuatio Tertia tells us that Otto married Lutgarde, who was from Namur, and had two sons. Their brother Arnulf is known from other records, so their children would be:
