I work with my brother and I don't care that its Christmas Eve, I'm going to have him fired.
Why would you want to do that to your brother, especially on Christmas Eve?
I want to get rid of him for being ungrateful, and I think he'll learn if he loses his job.
It is very important to be good to your family, even if he isn't perfect there are better ways to handle it than allowing him to lose his job on the day before Christmas. You could wait a few weeks, or even speak with him about his poor performance, but doing such a terrible thing will only hurt him mentally and could potentially hurt the rest of your family. I doubt you want that on your conscious.
He will be fine he has a family to help him through it.
No offense, but I think you're being callous towards your brother's feelings aren't truly grasping about how this will hurt him. In the spirit of the holidays I think you should give him a second chance and explain how his work performance needs to improve. Who knows, he might surprise you in a good way.