Vitali previously has hinted on retirement, after Adamek, unless Wlad loses a title defence, he will fight Haye/retire. They definitely will not fight. You've got a better chance of a wank off the pope.
Theyre usually in different weight classes Jmm / Rafael or there is usually a huge difference in talent Hatton, Morales and Manny's brothers. I cant really think of any others off the top of my head of two brothers at the very top at the same weight class.