[11] Sixtus's father, Prince Xavier of Bourbon-Parma, was the leader of the National Council of the Traditionalist Communion, the largest faction of Spanish Carlists, and thus claimed to be the rightful monarch of Spain (as "Javier I") from 1952 until his "abdication" in 1975.

[18] In 2016 Carlos told the Spanish press that, while (like his father in 2005) he "does not abandon" his claim to the throne, it is "not a priority" in his life, and he "will not dispute" [no planteo pleito] the legitimacy of King Felipe VI.

[3] Some of them recognize him as king, under the title Enrique V.[2] Sixtus himself has never explicitly asserted his right to the throne; rather, he has stated that he would prefer to remain regent in the hope that one of Carlos Hugo's sons may return to traditional Carlist ideology.

[citation needed] Although the youngest of six children and the second son of his parents, Sixtus inherited his childhood home, the chateau de Lignières near the middle of France, from his mother whose dowry it had been.

[4] In 2010, he sought a court order to prevent the continued exhibition of artworks by the Japanese artist Takashi Murakami at the Palace of Versailles.

[20] Sixtus was present at the episcopal ordination of four bishops who belong to the Society of Saint Pius X by Archbishop Marcel Lefebvre on 30 June 1988 at Écône, Switzerland, and was the first to publicly congratulate him.

In 2014 he took part in a far-right meeting in Vienna organised by Konstantin Malofeev, in which the participants (among others Aleksandr Dugin, Marion Maréchal-Le Pen, Aymeric Chauprade, Ilya Glazunov, Volen Siderov, Heinz-Christian Strache, Johann Gudenus, Johann Herzog and Serge de Pahlen) discussed about how to 'save Europe from liberalism and the "satanic" homosexual lobby'.

[22] In the context of the Syrian civil war, he has stated that Bashar al-Assad is the legitimate President of Syria and that the Arab Spring was an Anglo-American intervention to take control of the Middle East.