I suppose they could get DNA from his sons, both living and dead.

There is Omar Bin Laden who wanted to marry a woman in the UK. They were married but apparently he never got a visa. They lived in Egypt for a while, and then they tried to move to Spain. Their romance made it in an odd way, but he was 27 and she was 51 at the time.

http://www.timesonline.co.uk/tol/news/uk/article2056380.ece

http://www.ekimeeza.com/?p=2375

http://www.celebrifi.com/gossip/Osamas-Son-Omar-Bin-Laden-Wants-To-Date-Drew-Barrymore-3038832.html

Apparently he married another woman a year later or so. It seems that he has two wives. In September of 2010 he was living in Syria and described himself as "single", wanting to meet Drew Barrymore! If he volunteered DNA, they would have a sample to compare Y chromosome's with.

In 2009 a drone killed one of his son's in Pakistan. They could only be 80% sure that Saad Bin Laden was killed. If they truly killed him and they had a sample from that corpse they could compare Y chromosome's too. Difficult to do, because it was in a remote tribal area in Pakistan and sending somebody for just a DNA sample is a big risk. I suppose they could bribe a local to collect it.

http://www.timesonline.co.uk/tol/news/world/asia/article6724214.ece

Altogether, Osama Bin Laden apparently had 4 wives, and fathered from 12 to 26 children according to varied reports. Many of his children live in Iran under strict government control. I suppose that some of them could be sources of Y-chromosomal DNA.

One of his other sons, Khalid bin Laden, was also killed last week in the attack.

Some of his sons are jihadists, so there will be no shortage of replacements. I suspect it won't be lond before another Bin Laden, younger, healthier and full of hatred, will walk in his father's footsteps. I don't know if Hamza Bin Laden is alive, but apparently he is a true fanatic who recited poems of hatred against infidels. He grew up holding a kalashnikov.