I agree with Henry if you have more than two brothers, and you're referring to two of them. If you're referring to the *only two* brothers you have (and perhaps, you have sisters that you want to exclude from the sentence), then it's "my two brothers". Example 1: You have three brothers. Two are older than you, one is younger. "Two of my brothers are older than I am, one is younger." Example 2: You have three siblings. Two brothers are older, the sister is younger. "My two brothers are older than I am, and/but my sister is younger."

"Two of my brothers" is right