The legend of the Swan-Children seems to be in some way closely related to the region of Lotharingia (i.e., Lorraine), where some writers believe it originated.  Here at the Monastery of Haute Seille it was preserved in the early form mentioned above; and since the tale of the Swan-Knight was evidently then and there a familiar one, the theory that this also originated in that region may yet prove to be true.  It is interesting to note that the German name of the province, Lothringen, is the source of the name Lohengrin, which may suggest a reason for Wolfram von Eschenbach's identification of Parzival's son with the current story of the Knight of the Swan. (The Two Knights of the Swan, Lohengrin and Helyas, Jaffray, 1910).

   Knight of the Swan, Lohengrin, son of Parzival.  He went to Brabant in a ship drawn by a swan.  Here he liberated the princess Elsen, who was a captive, and then married her, but declined to tell his name.  After a time, he joined an expedition against the Hungarians, and after performing miracles of valour, returned to Brabant covered with glory.  Some of Elsen's friends laughed at her for not knowing her husband's name, so she implored him to tell her of his family; but no sooner was the question asked than the white swan re-appeared and conveyed him away.—Wolfram von Eschenbach (a minnesinger), Lohengrin (13th century). (Character Sketches of Romance, Fiction and the Drama, Brewer, v.4, 1902)