The languages are very similar! Hell, I speak french, and from this I can read spanish, latin and portugese usually. The languages are that similar. As for the names, just looking at the website, brynn is the very word for, or a word for hill/mound in the Welsh dialect, but Brian isn't a word, it is from the Old Celtic bre, and 'an' a common suffix was added to create a name. The common part, 'bre' is probably interelated between the languages.