Raphael is doing his bed not to sleep - which means he's also checking on others he's been keeping an eye on. He's always got an ear open for his, or his siblings' names, and hearing the earlier argument, he'd been watching. As soon as he realized the fight was actually serious, not just blowing off steam, he called out to Balthazar curtly, then used a (mostly gentle) wave of telekinesis to push them apart before flying in.