Linguistically, Breton's closest surviving relative is Welsh but whereas Welsh is enjoying complete endorsement of the state for the past couple of years (their way of saying "sorry", I guess), Breton is considered an almost dead language. It's also sad to see that there are many more endangered languages within Europe such as Provencal. I also read that Irish Gaelic wasn't doing too well.
I read reports that even though it's the official language of Ireland, a very limited number of people speak it in their daily life and that the Gaelic speaking area (the Western parts) are getting smaller day by day. I hope it won't come to that and Gaeilge will break through. Amongst Celtic languages apparently Scottich Gaelic has a rising rate of speakers, which is good to hear.