I have to attend the wedding of my boyfriends daughter. besides he and I his Ex's whole family will?

try to pretend its not awkward. Pretend it's a normal thing, and also your probably not the only who's had to deal with a situation like this so it''s not like letting a newly discovered animal bite you. I also advise you to pay attention to his Ex and their family, it might explain a little bit more about why they broke up. Also try to be in high spirits, try to keep the situation light. Insert yourself with his family to make it a little better. And i don't mean to panic you but weddings have been known to bring about the feeling of love. It's probably not likely that he would try to go back to her but it is possible. And also chances are it's not as awkward as you think it might be. It probable might just make your relationship stronger.