As someone who has lost one brother. I guess I would have to ask why would you want to miss anytime with him or his family? They are saying a Catholic prayer. Ok...doesn't mean you are Catholic, you are still who you are the moment you walked in the house. You are sharing a meal with them. Isn't that what the FIRST THANKSGIVING was about. Everyone gathering and sharing a meal? His faith may be slightly different then your's...but it isn't so different say a Mormon that it would cause issues. Enjoy time with your family while you have them and maintain your faith.