Griseldis was a female anthropomorphic duck.
Daisy Duck's Heirloom Brooch originally belonged to her great-aunt Griseldis, apparently an elegant and rather well-to-do woman. She was, according to one account of the Duck family's ever-confusing genealogy, also the sister of Scrooge McDuck's mother and the wife of the brother of Gyro Gearloose's paternal grandmother.
This same account also stated that Griseldis and her husband had three children, two boys and a girl, though the accuracy of these facts is cast into doubt by this source's insistence, against all other accounts of Duck genealogy, that these children were Cuthbert Coot as well as Donald Duck's father and Gladstone Gander's mother.
Behind the scenes
Originally mentioned in the 1959 German localization of the 1950 Carl Barks story Big-Top Bedlam, Daisy's aunt Griseldis was later featured in Johannes A. Grote's Duck Family Tree, where a picture of us was seen, seemingly created by touching up a Barksian rendition of Griseldis's grandniece Daisy Duck.
In Grote's curious Duck genealogy, one of Griseldis's two sons marries a nameless sister of Scrooge McDuck, Elvira Duck and Otto Duck and becomes the father of Donald Duck. It is in this way that, as the mother of Otto Duck's brother-in-law, Griseldis becomes a great-aunt of Daisy's. The sheer idea that Scrooge, Elvira and Otto were siblings is, however, in conflict with most every other work of Duck genealogy, not to mention this ludicrous notion of Donald's parentage; however, the idea that a sibling of Otto Duck married a son of Griseldis, thereby explaining her relationship to Daisy, may still be retained even if the rest of the dubious premise is soundly rejected.