I don't want to attend my cousins wedding
Why don't you want attend your cousin's wedding?
I don't feel like they will be a good match and would rather them break up.
It is good to attend the important events in your family's life. If you do not you may regret it later.
I'm going to question my relatives on their reason for being against my marriage
If you are going this in retaliation for how they treated you is unfair. You should work through your your issues and try not to ruin someone else's big day.