Here is a video of Karl and Zita's wedding day, reportedly one of the first royal wedding celebrations to be captured on video. I quote an account of the events, as told by Arturo E. Beeche of Eurohistory:
"The wedding day, October 21, 1911, was indeed memorable. Absent were the strict pomp and circumstance of the Viennese court, and instead witnesses recalled that the event seemed like a 'family party...such as one sees when the daughter of a local landowner marries.' Schoolchildren, in their nicest attire, lined the road from the train station to Schwarzau to greet the automobile transporting Emperor Franz Joseph, who was rather pleased by this greeting from among his youngest subjects.
"At the entrance to the Schloss Schwarzau Archduke Karl and the Duke of Madrid, as Head of the House of Bourbon, awaited the arrival of Emperor Franz Joseph. The Emperor was warmly greeted and quickly taken inside, where Dowager Duchess Maria-Antonia and Princess Zita greeted him. Franz Joseph gently kissed the hand of Maria-Antonia and instead of doing the same with Zita, he gave her a grandfatherly embrace. It was his way of welcoming the beautiful Bourbon princess into his family's fold.
"The wedding procession began soon afterwards. Archduke Karl walked between his mother, Archduchess Maria Josepha, and Emperor Franz Joseph. Zita followed, flanked by her own mother and by the Duke of Madrid.... Zita recalled: 'Don Jaime, the Duke of Madrid, who had unsuccessfully sought my hand in marriage, walked me to the altar. Proudly, he wore a superb Russian uniform, but my brother Sixtus deflated his ego when he asked don Jaime, "Pardon, but are you dressed for the circus?" What the very proper Duke of Madrid answered to this smart comment we do not know, but can easily imagine."
We have a chance to see the Duke of Madrid, among others, in the video (standing next to Karl at 0:30-0:35, close up at 1:06-1:07, and later on).... His uniform
was over the top, but I can't help thinking that it was also very generous of him to walk Zita to the altar (when her father had died), especially given that he had courted her unsuccessfully. And the bride & groom look lovely & kind.
YouTube - Wedding Emperor Charles I of Austria & Zita / Hochzeit Kaiser Charles I von Österreich und Zita