Martin DeWitt married Ellen Douthel. Their children were: "Captain" William DeWitt m. Mary Devonald (I have a genealogy on this branch) John DeWitt m. Mary Unknown (I have a partial genealogy on this branch) Thomas DeWitt Harris DeWitt m. Elizabeth Brockington and 2nd ??? Pawley (I have a partial genealogy on this branch)
Is it your belief that this Thomas DeWitt married Susannah Allen?If so, do you have any documentation you can share?
It is know that the DeWitt and Allens lived near each other in Virginia and some members of both lines moved to the Cheraw area.It's certainly possible that there were a number of marriages between the two families.