Britannian Imperial Family

The Holy Empire of Britannia is ruled by the Imperial family, descended from the British Royal Family, which holds the highest positions within its government and military. The prince and princesses are ordered by number, which is determined by the status of their mothers, the imperial consorts. For example, Clovis is the Third Prince while Lelouch is (or was formerly) only the Eleventh Prince. The numbering of the Imperial princes and princesses is sorted by gender and birth order. For example, Euphemia is the third born daughter, making her Third Princess and Clovis is third born son, making him Third Prince. The princes and princesses use the same nobilty particle as their mother, though the usage does not mirror any real-world method. The female members are entitled to elect a personal guardian called a "Knight," who are given authority and placed directly under their command, with their own unit. Cornelia's Knight is Guilford who, along with her, commands a unit of Knightmare Frames. Suzaku Kururugi also served as personal Knights to Euphemia, and Lelouch after the latter became emperor. It can be assumed that there are more members in the imperial family as there is a gap between the Third and Eleventh Princes. Though not explicitly stated, Nunnally was likely Fourth Princess during her father's reign, but with the gap between Third and Eleventh Princes, this cannot be said for certain.

Britannian Imperial Family

 * 91st Emperor Alec la Britannia
 * 98th Emperor Charles zi Britannia
 * First Prince Odysseus eu Britannia
 * First Princess Guinevere su Britannia
 * Second Prince Schneizel el Britannia
 * Second Princess Cornelia li Britannia
 * Third Princess Euphemia li Britannia
 * Fifth Princess Karine le Britannia
 * Imperial Consort Gabrielle la Britannia
 * Third Prince Clovis la Britannia
 * Imperial Consort Marianne vi Britannia
 * 99th Emperor/Eleventh Prince Lelouch vi Britannia
 * 100th Empress Nunnally vi Britannia

Other members of the Imperial Family
Castor and Pollux rui Britannia are a pair of twin princes introduced in the Code Geass video game for Nintendo DS. Repeat playthroughs of the storyline add them as new antagonists to allow the recruitment of Cornelia and Euphemia, as well as certain other Britannian officers.
 * Castor rui Britannia
 * Pollux rui Britannia