Pawpaws spread aggressively by suckers, but are surprisingly bad at getting pollinated. It is probably a clonal patch. There is also a possibility they aren't getting pollinated. (They are pollinated by beetles and flies).

You'd probably have more luck if you buy a potted or bare root Pawpaw and plant it nearby. You can get them at "Edible Landscaping". When it gets big enough, you would get fruit on the nearby trees. That could take years, though.

The other option is you could try manually pollinating some flowers with a feather duster. Or hang pieces of meat from the trees in the spring to attract the beetles and flies they use to pollinate them.

Here is a link that might be useful: Edible Landscaping

istock1,
check out my post on pawpaw.
Last week I collected a 5 gallon bucket of fruit along the road leading into Port Deposit MD (Cecil County). I could have done without the dead snapping turtle :(
The foliage hides the fruit. Go up to the tree, shake it hard, and notice where the fruit falls. If you find a patch that doesn't make fruit, simply go on to the next one.

Here is a link that might be useful: Really Stepped in it thread

Thanks you all for the information!