Why wont my boyfriend let me meet his family?

We've been together for over a year now. (Anniversary was in November). Anyways, I've only meet his mom dad and his two sisters, but one of which I've seen once. I barely know anything about them.

There was a change on the 4th of July, everybody was going to be there but he said he wasn't in the mood to be bombarded with questions and he promised I'd meet them in Thanksgiving or Christmas. I told him I understood where he was coming from and agreed in the compromise.

When Thanksgiving came around I asked if I was meeting them and he said idk. A little while later I heard him and his mom talking about their Thanksgiving party the next day. So I asked him about it and he said id meet them at Christmas for sure.

Now that it's Christmas he said I'm not meeting them. He has three Christmas things. One with just him and his parents. One with the sister that i sort if know ( Wich is the one I'm apparently going to) and finally one with everybody. He claimed it was his mom he planned it and put me in the one with the people i already know. However, ik that he was talking to his mom about Christmas before and I'm pretty sure if he would have just asked she'd I could come to the other one.

We were arguing about it last night and he said that I was the one who insisted on getting people gifts. I only got his mom sister and niece presents because they got me stuff and I told him that and if it was going to be a big deal I didn't have to give it to them during the party and could do it before or something.

I don't get why he won't let me meet them. Is it that he's like embarrassed by me or something? Or am I just overreacting? Thoughts?