Question: are welsh and breton mutually intelligible?
Answer: Welsh, Cornish, and Breton are each no more than 55% mutually intelligible, and Irish Gaelic/Scottish Gaelic share somewhere between 65–75% mutual intelligibility, Manx is only about 50% intelligible to either. ... Welsh, Breton, and Cornish are obviously related, and to no small extent mutually intelligible.