The Groa of the myth is mentioned in two other places: in Groagalder and in Gylfaginning. Both sources agree in representing her as skilled in good, healing, harm-averting songs; both also in describing her as a tender person devoted to the members of her family. In Gylfaginning she is the loving wife who forgets everything in her joy that her husband, the brave archer Orvandel, has been saved by Thor from a dangerous adventure. In Groagalder she is the mother whose love to her son conquers death and speaks consoling and protecting words from the grave. Her husband is, as stated, Orvandel; her son is Svipdag.
If we compare the statements in Saxo with those in Groagalder and Gylfaginning we get the following result:
Saxo: King Sigtrygg has a daughter Groa. Gylfaginning: Groa is married to the brave Orvandel. Groagalder: Groa has a son Svipdag. Saxo: Groa is robbed by Gram-Halfdan. Saxo: } Hostilities on account of the robbing of Hyndluljod: } the woman. Gram-Halfdan kills Skaldskap.mal:} Groa's father Sigtrygg. Saxo: With Gram-Halfdan Groa has the son Gudhorm. Gram-Halfdan is separated from Groa. He courts Signe (Almveig in Hyndluljod; Alveig in Skaldskaparmál), daughter of Sumbel, king of the Finns. Groagalder: Groa with her son Svipdag is once more with her first husband. Groa dies. Svipdag's father Orvandel marries a second time. Before her death Groa has told Svipdag that he, if need requires her help, must go to her grave and wake her out of the sleep of death. The stepmother gives Svipdag a task which he thinks surpasses his strength. He then goes to his mother's grave. From the grave Groa sings protecting incantations over her son. Saxo: Svipdag attacks Gram-Halfdan. After several conflicts he succeeds in conquering him and gives him a deadly wound. Svidpdag pardons the son Gram-Halfdan has had with Groa, but persecutes his son with Signe (Alveig).
In this connection we find the key to Svipdag's irreconcilable conflict with Gram-Halfdan. He must revenge himself on him on his father's and mother's account. He must avenge his mother's disgrace, his grandfather Sigtrygg's death, and, as a further investigation shows, the murder also of his father Orvandel. We also find why he pardons Gudhorm: he is his own half-brother and Groa's son.