My parents got me concert ticket for my birthday and I'm not going to use them.
Is there a reason why you will not use the tickets?
They got tickets for me to go with my cousins, and I don't really like them.
Hopefully you had a good birthday! It seems that your parents spent quite a bit of money on those tickets, and it would be ungrateful for you to use them. Give it a chance, maybe you'll realize your cousins aren't so bad.
Eh.
This seems to me to be forced to do a thing that you don't want to do, as grateful is a good default, it's important to note motives. Don't do anything you don't like or anything that takes you aback, A gift might not be one.