I think your girlfriend should have stepped in years ago and told her family that they need to accept you and treat you well as she was going to be with you no matter what they thought. But I do understand the jealousy feeling. It’s like your girlfriend is in a tug of war between family and you. I’m sure you feel left out when your girlfriend goes to visit family and it would be much easier if you could go with her and have a good time, too. Maybe the both of you should go to couples counseling and try to resolve all of these issues. After 6 years, her family should have accepted you.