if Brad wanted to pass on his generations but if his wife doesn't want babies or is too busy to have one, and if Brad do have a brother or more, and his brother do have sons, which means that Brad do have nephews so I guess he doesn't need to worry since his nephews would carry on the "pitt" generation or something like that...
so if you really wanted to pass on to the next generation, but since your wife couldn't do that, but your brother is married and have a son or two, then you don't need to worry about it anyway...right? alot of guys who are husbands and fathers always wanted their "last name" to continue forever and stuff like that...but hell, nothing last forever anyway.