DNA testing?

I heard they had DNA from a family member already. They just need to compare the samples. But you know the pictures or a video will be leaked to the press!

His dead sister, iirc.

He's right. They did a DNA test off of a stored sample of Bin Laden's dead sister's DNA, and they determined it to be enough of a match to confirm it being him.

I believe they have one of his children in Gitmo...

The Bin Laden's are a large family, and not all of them agree with Osama's actions. I'm sure it wouldn't be hard to get DNA from one of them.