His name was Kieren Kiely & he was born in 1977 in County Cork. He was brought in for the BH tour & also played in their last group appearances in 2005 like Live 8 as well as playing accordian on a few tracks on "Home".
Since then, he is known to have worked with Sinead O'Connor. Will he be part of the lineup of the "returning" Corrs ?? Somehow I don't think so, although they MAY call on him for recording should any track need accordian.