Queen Katerina was the first wife of King Garon of Nohr. With him, she had a son named Xander, who is the eldest of the Nohrian royal siblings. Xander also happens to be the only child of Garon who was not born to a concubine. Katerina died some time before the start of Fates when the Nohrian children were extremely young. After her death, King Garon remarried to Arete, Azura's mother.
According to Elise's nanny Cassita in the Birthright route, Katerina was very beautiful and was well loved in Nohr. Camilla, the eldest daughter of the Nohrian royal family, also mentions her in the Revelation route while describing Azura's past in Nohr. Due to Katerina's popularity in Nohr, Arete and Azura were not generally accepted as members of the royal family, and Xander, Camilla, and Leo were instructed not to associate with their stepsister.
Katerina and Ekaterina are variants of the name Catherine. Ekaterina is the Bulgarian and Macedonian form of Catherine, and a variant of the Russian transliteration of the name Yekaterina (Екатерина). The name originated from the Greek Αἰκατερίνα or Αἰκατερίνη (Aikaterina, Aikaterinē), which is of unknown etymology. The name subsequently came to be associated with the Greek adjective καθαρός (katharos), meaning "pure".