Young is a pain! First you will need one union with extremelly high HP so it can survive his technique Brawl. Have one union hold up Young and have the others attack his subordinates because it's better to kill 1 or 2 than have all of them nearly dead. When he's low on HP he will cast Miracle which gives him enough strength to one-shot a single union! So have plenty of healers and he'll die eventually. Good luck, hope you beat him!