I'm going to mention my divorce at my brother's wedding
Why would you mention your divorce?
Because I'm not happy to see him married.
It's rude to want to actively ruin someone elses mood. If you have an issue with him maybe you should talk directly to him?
I'm not going to talk to him because I don't care about him, he's a loser. I'm going to ruin his day and I don't give a shit.
You shouldn't actively try to bring down your brother's wedding. Maybe you shouldn't go at all if you plan on making a scene.