Too much Drama?

When people tell actors to 'break a leg' as a way of saying good luck before a performance, they don't mean it!  The entire cast of 'Joseph' was devastated when Joseph himself injured his leg, and had to be taken off to hospital.  However, undeterred, everyone got behind Cormac Nellis who stepped in as understudy and did a fantastic job.  The icing on the cake was that Joseph, alias Michael O'Brien, was at his post back stage, playing bass in support of the band.  But who was the bearded mystery brother who took on Cormac's original role?