No one can prophecy exactly what will happen, but usually an older tup fits in well with a group of younger tups, with minimal fighting, just to show them who's the new boss. We do this every year - last year's meat tups go off round about now, and the new season ones are taken off their mums before the end of August and put in with the older boys. The older tups chase them round a bit, just in case they are females in disguise, but it all settles down to peace and boys talk for the winter.