Hi Catherine, I certainly hope that you can find some leads! I do think that adoption papers might prove interesting also and give you much information - You can check with your state to find out about your possible sister if you know her approximate date of birth - they would not let a stranger have records, but a sister could. I believe there is a fee. Another source would be census records - you could ask about that at the library. They are done every 10 years, so you might find your folks in one of them, and maybe more. Ask around at the library - in the genealogy section - or write your State Archives and ask some questions. Get on mailing lists for ALLEN through www.rootsweb.com It is amazing what may pop up - sometimes it takes a couple of years, but then things just "happen.!"Interestingly - our son is David Allen Coleman, named after my Allen ancestors. I also have a second cousin with the same name: David Allen Van Norden! And the funny thing is - they were born about the same time! Small world, eh!
If I think of anything else, will pass it along - And don't forget the group called "Random Acts of Kindness" on the internet - they have done some fantastic things with their "know-how" -