They leave me out all the time, is it my fault?

[Alicia]

I have a group of cousins that are all close, they go out a lot and I'm always left out. The times I'm invited is when at family gatherings (when my parents are invited).
They have photos on Facebook of them all together, I don't even get asked.
When my cousin came here from canada I spent 2 weeks with my cousins and on the day he was leaving, I went home. I saw him at a family gathering a week later. Why didn't they tell me? They didn't want me around?
A month ago I was asked to go on a road trip with them, they said they would let me know when it's happening but they never did and just went without me.
I rarely go to family gatherings anymore cause I feel like they don't want my company. My parents always make me feel so bad about it, they say that I'm not putting in any effort to be close with them. What do I do? I feel bad but at the same time I feel like I'm being rejected every time I try. Any thoughts on this?