I have reason to believe that the AI defaults to certain names and tends to make use of specific first and last names when generating characters. You can easily see this in the AI Character Generator when using the "Persona/Chat" feature that basically turns your generated images into actual characters you can chat with in the ACC. This only really applies to the old model, the new model is actually more creative with names.

Mainly, when generating characters with the "anime" art style, it'll generate Japanese names for the character. Or if generating furry characters (e.g. an anthro wolf), it just defaults to generic names like Luka or Kaira or Kara or some variation or form.

But I assume you're not using this feature but instead using the "Unknown" character that automatically generates characters based on a prompt. One pattern I DID notice here was that most characters had the last name "Castellanos" which was weird but I didn't really care much for it.