So before the wedding, the King sends his children to a hidden castle in the forest, secretly visiting them by following a magical reel of thread given to him by a wise woman.

Mistaking her for their father, the six princes rush out to greet their stepmother who then throws the shirts over her stepsons, transforming them into swans.

They tell their sister that they have heard of a way to lift the curse: she must not speak for six years while sewing six star-flower shirts for her brothers.

The Princess agrees to do this and, sheltering in a tree, dedicates herself solely to gathering the star-flowers and sewing the shirts in silence.

Folklorist Stith Thompson points that the stories of the Aarne–Thompson–Uther ATU 451 tale-type follow a long literary history, beginning with the tale of the Dolopathos, in the 12th century.

Fairy tale scholar Jack Zipes cites that the Brothers Grimm considered an origin in Greco-Roman times, with parallels also found in French and Nordic oral traditions.

[13] French scholar Nicole Belmont identified two forms of the tale type in Europe: one "essentially" present in the Germanic area and Scandinavia, and another she dubbed "western version".

She noted that in this western version, the youngest sister, after she settles with the brothers, asks for fire from a neighbouring ogre, and a tree sprouts on their yard and bears fruit that causes the transformation.

In other European variants, the number of princes/brothers alternates between three, seven or twelve, but very rarely there are two,[20] eight,[21][22] nine, ten or even eleven,[23] such as the Danish fairy tale collected by Mathias Winther, De elleve Svaner (English: "The Eleven Swans"), first published in 1823,[24][25] or Ligurian tale Les onze cygnes.

[26] Hungarian folk tale collector Elisabeth Sklarek compiled two Hungarian variants, Die sieben Wildgänse ("The Seven Wild Geese") and Die zehn Geschwister ("The Ten Siblings"), and, in her commentaries, noted that both tales were related to the Grimm versions.

[29] Commenting on the Irish variant collected by Patrick Kennedy, Louis Brueyre indicated as another variant the Indian tale of Truth's Triumph,[30] or Der Sieg der Wahrheit: in the second part of the tale, the youngest child, a girl, witnesses the transformation of her one hundred brothers into crows.

[31] In a Lithuanian variant, Von den zwölf Brüdern, die als Raben verwandelt wurden[32] or The Twelve Brothers, Twelve Black Ravens, the witch stepmother asks for her husband to kill his sons, burn their bodies and deliver her the ashes.

Their sister has a dream where an old woman tells her the key to reversing the curse: weaving coats with leaves from the acacia tree she is placed on by her brothers after fleeing home.

[35] The other variation is in the result of the brothers' transformation: in some versions they are ducks, in others ravens, and even eagles, geese, peacocks, blackbirds, storks, cranes, jackdaws or rooks.

[47] Folklorists Johannes Bolte and Jiri Polivka, in their commentaries to the Grimm fairy tales, compiled several variants where the brothers are transformed into all sorts of beasts and terrestrial animals, such as deer, wolves, and sheep.