According to Saxo Grammaticus, Hrolf Kraki's great-uncle Frodhi was Hadding's son Frodi whereas, according to Poul Anderson's Hrolf Kraki's Saga, the great-uncle Frodhi was a son of Frodhi the Peace-Good. Many generations of Skjoldungs preceded the Peace-Good because we are told that one on them long ago was Hermodh, ancestor of Grendel.
At some point, which I can't find right now, in Anderson's War Of The Gods, Hadding names his grandfather as Skjold. Does this mean that he is claiming to be that close in time to the Skjold who was a son of Odin and the founder of the dynasty? I think it is more likely that this is another case of two men with the same name but will see if I can delve deeper into the Skjoldung lineage.