He's terribly jealous of an ex-boyfriend. Now my boyfriend is threatening not to come to my parents' place at all. I really want these two to get along. Girl Dear Lover Girl, I assume you've tried talking sense, explaining facts, making reassurances and so forth. I'm sure it didn't work.
Reason has little power against such morbid fantasies.
Offer to fire up the microwave, open a can of jellied cranberry sauce and snuggle in sleeping bags in front of the tube. Show him who you really want to be with when the biggest social event of the season is just for you and him. I don't take care of my appearance any more. That's the problem.