The Völsunga Saga on Giuki
The Story Of The Volsungs, (Volsunga Saga) > CHAPTER XXV. Of the Dream of Gudrun, Giuki's daughter.
relationship: King Giuki ruled south of the Rhine and had three sons: Gunnar, Hogni, and Guttorm, and a daughter Gudrun
"There was a king hight Giuki, who ruled a realm south of the Rhine; three sons he had, thus named: Gunnar, Hogni, and Guttorm, and Gudrun was the name of his daughter, the fairest of maidens"
relationship: Giuki's wife was Grimhild, a woman skilled in sorcery
"Giuki had wedded Grimhild the Wise-wife"
The Story Of The Volsungs, (Volsunga Saga) > CHAPTER XXVI. Sigurd comes to the Giukings and is wedded to Gudrun.
attestation: Giuki offered Sigurd his daughter Gudrun and a share of dominion without being asked
"both dominion shalt thou have, and our sister freely and unprayed for, whom another man would not get for all his prayers."
attestation: Giuki tells Sigurd he gives them great good and strengthens their realm with exceeding strength
"Great good thou givest us, Sigurd, and with exceeding strength thou strengthenest our realm."