Hrothgar and Hróar
As for the king of the Danes, Hroðgar, he is identical to Hróar or Ro, the uncle of Hrólf Kraki who in other sources outside of Beowulf rules as a co-king with his brother Helgi. But in those sources it is Hróar/Hroðgar who dies before his brother or who departs to Northumberland to rule his wife's kingdom leaving Helgi/Halga the sole rule of Denmark. In Beowulf Halga/Helgi has died and Hroðgar is the primary ruler with Hroðulf son of Halga as a junior co-ruler.
Furthermore, the Swedish kings referenced in Beowulf are adequately matched with the 5th and 6th century Swedish kings in Uppsala (see also Swedish semi-legendary kings): This has obviously nothing to do with a common origin of the Beowulf and Hrólf Kraki legends in particular but simply reflects a shared genealogical tradition.
| Beowulf | Hrólf Kraki, Heimskringla etc. | Relation |
|---|---|---|
| Ongenþeow | Egil (Angantyr) | father of Ottar and Ale |
| Ohthere | Ottar | brother of Áli |
| Onela | Áli | brother of Ottar |
| Eadgils | Adils | son of Ottar |
Read more about this topic: Beowulf And Hrólf Kraki