Thomas R. Duncan was full brother of my great great grandfather Peter Hutsell Duncan, and half brother of my great grandfather Albert E. Duncan. As far as I can tell, he was the oldest child of William Duncan and Amanda Hutsell Duncan. A good part of his biography has been listed here in his Find A Grave memorial, and it was insrumental in me learning more about my ancestor, Peter too, since they went to Kansas together. There are also tidbits of info about William included, which seems to be all anyone knows about William, as I see it repeated almost word for word in any files about William.
Thomas' biography can also be found in The History of Cherokee County Kansas.