This second Halfdan the Old is father of Jarl Ívar of the Uplands who married a daughter of a certain Eistein and so became father of Eystein the Clatterer (Eysteinn Glumra) who was father of Jarl Rögnvald of Møre and of Rögnvald's brother Sigurd, and also of two daughters: Svanhild who was one of King Harald Fairhair's wives and another daughter named Malahule. According to various sources, Jarl Rögnvald had three illegitimate sons: Hallad (Hallaðr), Hrollaug (Hrollaugr), and Torf-Einarr. Later, by his wife Ragnhild (Ragnhildr) daughter of Hrólf Nose (Hrólf Nefja), Rögnvald was father of three legitimate sons: Hrólf, Ívar, and Thórir (Þórir) the Silent. Hrólf, also called Ganger-Hrólf (Gǫngu-Hrólfr 'Hrólf the walker'), Icelandic/Norwegian historians identify him as the Rollo who conquered Neustria which was then renamed as Normandy, but that identification seems very doubtful. Thórir inherited his father's lands. The first four Jarls of Orkney were successively Rögnvald's brother Sigurd, Sigurd's son Guthorm (Guttormr), Rögnvald's son Hallad, and Rögnvald's son Turf-Einar. From Turf-Einar the later Jarls descended. Hrollaug and his wife and sons settled in Iceland.
[source Wikipedia http://en.wikipedia.org/wiki/Halfdan_the_Old]
