I want to show up to my cousin's wedding wearing dirty clothes.
What makes you want to do something like that?
I don't really like my cousin very much.
Family get togethers can often be stressful. It is still unacceptable to show up at a family event such as a wedding in dirty clothing.
Tell that to my brother, I know he'll always back me up.
If you can't follow the dress code you should just stay home. If you have nothing to wear you can ask your family to help you rent a suit or find a shirt and pant.