text: The extreme length of Æthelberht's reign also has been regarded with skepticism by historians; it has been suggested that he died in the fifty-sixth year of his life, rather than the fifty-sixth year of his reign. This would place the year of his birth approximately at 560, and he would not then have been able to marry until the mid 570s. According to Gregory of Tours, Charibert was king when he married Ingoberg, Bertha's mother, which places that marriage no earlier than 561. It therefore is unlikely that Bertha was married much before about 580. These later dates for Bertha and Æthelberht also solve another possible problem: Æthelberht's daughter, Æthelburh, seems likely to have been Bertha's child, but the earlier dates would have Bertha aged sixty or so at Æthelburh's likely birthdate using the early dates.
  Gregory, however, also says that he thinks that Ingoberg was seventy years old in 589; and this would make her about forty when she married Charibert. This is possible, but seems unlikely, especially as Charibert seems to have had a preference for younger women, again according to Gregory's account. This would imply an earlier birth date for Bertha. On the other hand, Gregory refers to Æthelberht at the time of his marriage to Bertha simply as "a man of Kent", and in the 589 passage concerning Ingoberg's death, which was written in about 590 or 591, he refers to Æthelberht as "the son of the king of Kent". If this does not simply reflect Gregory's ignorance of Kentish affairs, which seems unlikely given the close ties between Kent and the Franks, then some assert that Æthelberht's reign cannot have begun before 589.
  While all of the contradictions above cannot be reconciled, the most probable dates that may be drawn from available data place Æthelberht's birth at approximately 560 and, perhaps, his marriage to Bertha at 580. His reign is most likely to have begun in 589 or 590.