Jen, there is nothing else you can do. Were they wild/feral? I have come to the conclusion that some cats just stay that way no matter what you do. You may eventually get them to come around to you but probably not strangers. If someone adopted them they would need tons of patience and they still may not ever be *lovable* kitties.
On the other hand!! Just about the time you give up they may just walk up to you and become loving lap babies!!!
Go figure!! A cat is a cat and does what it does for reasons unknown!!
If they end up socializing with you only then I guess you will just have to add these two beauties to your personal pride!!