Oh right. I guess I always imagined that they spoke some variant of Russian on Barrayar but I guess it could be English as well unless Bujold is just being neglectful in her punctuation and Miles got English from Beta. Anyway it seems like those are the main Barrayaran languages that survived from Earth. Since there is a Lairouban language I suppose that some colonies or planets have developed new languages as well. Is Betan its own language or just a variant of English, or possibly some other language?

Remember that it was just a thousand years ago that all of Scandinavia spoke the same language. It wasn't until we truly started to settle that languages really diversified. I can still easily speak Swedish with a Norwegian or Dane and be understood. And probably get the main gist out of a German text as well.