1) what will umpire announce? in sosa-souza it was the country name after the last name. however, this won't help here.
2) when did it happen in ATP history that 2 brothers faced each other?
ad 2) bryans faced each other 4 times: http://www.tennisabstract.com/cgi-bin/player.cgi?p=BobBryan&f=ACareerqq&q=MikeBryan
George Foreman named all 5 of his sons George. Gary Payton has 2 sons who are both named GaryYes, full names is the answer. The Sousa/Souza problem was that they both had the same forename, so the country had to be used. I don't think anybody would ever be daft enough to name two sons exactly the same!