Baptism and Marriage Records for Charles I of Austria
Due to the popularity of genealogy in recent years many documents from lands that comprised Austria-Hungary are now available online. This has resulted in many royal and noble records coming along, because the parish registers were for pauper and prince alike.
These are the birth and marriage records for Charles I of Austria. If you'd like to see them, I can share those of other family members.
Birth / Baptism
https://data.matricula-online.eu/en/oesterreich/st-poelten/persenbeug/01%252F04/?pg=76
Birth: 17 August 1887, Persenbeug 1 (Château)
Baptism: 19 August 1887, Church of the Holy Florian and Maximilian, Persenbeug
Name: Charles Francis Joseph Louis Hubert Geore Otto Maria
The columns are Catholic/Protestant, Male/Female, Legitimate/Illegitimate
Father: His Imperial and Royal Highness, the Most Serene Prince and Lord Otto Francis Joseph, Imperial Prince and Archduke of Austria, Royal Prince of Hungary and Bohemia etc. etc., Knight of the Golden Fleece, Knight Grand Cross of the Spanish Order of Charles III and the Royal Saxon Order of the Rue Crown, First Lieutenant in the Royal and Imperial Dragoon Regiment "Alexander, Prince of Hesse and by Rhine N.6", son of His Imperial and Royal Highness the Archduke Charles Louis.
Mother: Her Imperial and Royal Highness, the Most Serene Princess and Lady Archduchess Mary Josepha, née Royal Princess of Saxony, Lady of the Order of the Rue Crown, daughter of His Royal Highness the Prince George of Saxony
Note below name: Died on 1 April 1922 in Funchal on Madeira in exile as the last Emperor of Austria.
Godparent: Charles Louis, Imperial Prince and Archduke of Austria, Royal Prince of Hungary and Bohemia etc. etc. etc.
Marriage to Zita of Bourbon-Parma
https://data.matricula-online.eu/en/oesterreich/wien/schwarzauamsteinfeld/02-06/?pg=72
21 October 1911, Schwarzau am Steinfeld
Groom: His Imperial and Royal Highness Charles Francis Joseph Louis Hubert George Otto Maria, Imperial Prince and Archduke of Austria, Royal Prince of Hungary and Bohemia etc., Catholic, single, of legal age, born in Persenbeug, Lower Austria, on 17 August 1887, legitimate son of His Imperial and Royal Highness Otto Francis Josef, Imperial Prince and Archduke of Austria, Royal Prince of Hungary and Bohemia etc., and Her Imperial and Royal Highness Mary Josepha, Imperial Princess and Archduchess of Austria, Royal Princess of Hungary and Bohemia etc., née Princess of Saxony.
Bride: Her Royal Highness Zita Mary of Grace Adelgunda Michaela Raphaela Gabriella Josephine Antonia Louisa Agnes of Bourbon, Princess of Parma, Catholic, single, a minor, born in the Villa Pianore in the parish of Capezzano in Lucca in Italy on 9 May 1892, legitimate daughter of the deceased His Royal Highness and Serene Lord Robert of Bourbon, Infante of Spain, Duke of Parma, and Her Royal Highness and Serene Lady Mary Antonia, Duchess of Parma, née Infanta of Portugal (Braganza).
Columns next to them are Catholic/Evanglical, age, Single/Widowed.
Correction below Zita say that her full name on the baptism certificate is: Zita Mary of Grace Adelgunda Michaela Gabriella Josephina Antonia Louisa Agnes Stanislava Anna Margaret Philomena Adelaide Roberta Vincentia Francisca.
Witness 1: Frederick Augustus, King of Saxony
Witness 2: Archduke Franz of Austria-Este
They were granted a dispensation in the "4th degree of consanguinity." I think that's because of their shared descent from Francis I of the Two Sicilies (via different marriages), which the closest blood link I could find.