On 16 April 1917, at the age of two, Robert was created Archduke of Austria-Este by his father, the Emperor. Archduke Robert was thereby chosen to preserve, in the form of a distinct secundogeniture, the Habsburg-Lorraine representation of the once-sovereign Duchy of Modena which had belonged to the House of Este. He was thus made heir to his assassinated relative Archduke Franz Ferdinand of Austria, (1863–1914), who had inherited in 1875 the Austria-Este designation and what had been salvaged of the Este fortune when the duchy was annexed to Italy in 1860.

Archduke Robert descended through his Habsburg father from Ercole III d'Este, Duke of Modena, and his mother Zita was a descendant of Maria Beatrice d'Este, heiress of Modena and her husband, Archduke Ferdinand of Austria. Thus the lineage of the last Este dukes, in female descent, remained joined to the Austria-Este legacy. Archduke Robert eventually adopted use for himself and his descendants in male line the surname Austria-Este, and he took also the title Duke of Este, intended henceforth to be borne by the head of the Austria-Este branch of the House of Habsburg-Lorraine.

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