I have checked our Patriot Index for all Blackwell men. There were 29 with the following names: Benjamin, Elihah, Francis, Jacob, 6 John's, 4 Joseph's, Joshua, Micah, 3 Robert's, 2 Samuel's, Stephen and Thomas. No Joel, Daniel or Isaiah. This may not mean they didn't serve, just that no one has entered DAR on those men. With as much information as you gave, you are well on your way to establishing Joel. Only the descendants of Daniel and Isaiah would be eligible for DAR membeship through those men since we are direct lineal descent organization.
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This free look up service provided by volunteer members of the DAR.