If they did a DNA test against his sister, wouldn't his brother also match? I'm no biologist but it can only check that the two specimens have the same parents, right?
Mitochondrial DNA should match.
In any case, there exists a test that would confirm his identity given we trust the identity of his sister.
I just don't care though. I don't see why anyone cares. It sickens me that there are people celebrating any sort of death. I see little difference in celebrating bin Laden's death and Taliban troops celebrating the death of an American soldier. Both are disgusting. Death is nothing to be happy about.
I think someone else in this thread said this, and I completely agree with it. There's no objective benefit to bin Laden being dead (other than political popularity, maybe). If anything, there are objective disadvantages.