Bring your brother. Feel free to tell them individually so it's two family members against one. Don't come out at the holidays or a funeral or any other time that's already stressful for the family. Tell them in a very private location, no restaurants or front porch, not even anywhere they can be seen. Having your child announce that they are gay can be an uniquely embarrassing experience for some parents.
As to what to say, speak English, or whatever language is spoken in the home. The point is your words need to be your own, the words of their child. They do need to understand that telling them is very hard for you. They need to understand that your telling them is your attempt to give them the honesty they deserve. They need to know they didn't gay you up with some obscure parenting mistake, that it is the person you were born to be. They need to understand that this isn't a change, that you've been gay and hiding it for a long time and that you aren't going to un-gay, it is who you are.
Be prepared for rejection. You've kept a huge secret from your parents. It has to shock them and put them off balance to some degree. If coming out goes badly back off graciously. Once the realization of what you've told them sinks in your parents are very likely to think more clearly on the situation and come to terms one way or another.