David, I don't know your Mortimer, however I have a theory you might want to check out. If your confident of the birthdate of feb 1786, I know he could not have been a child of William and Bersheba Watts Gulledge (one of the most prominent Gulledge lines of the time in the NC area) because William had a son Stephen Malichi in 1786. However since Willima was in NC and his family had later association with TN and AL it would reason that Mortimer might be a cousin to Stephen and thus William and Mortimer's father might have been brothers.
William had a known brother Jeremiah Gulledge who married a Elizabeth (unknown last name to me). Jeremiah was born abt 1740 in Isle of Wright VA, but as I said his brother William also born in VA moved to NC as it is believed their father Edward did as well (possibly with another sibling of William and Jeremiah named Thomas.) Jeremiah was known to have had at least four sons, Obediah, William Hood, Eldred and Frederick. I know nothing of the progeneters of Eldred or Frederick.Perhaps your Mortimer Frederick is Jeremiah's Frederick?Obidiah was born abt 1790, so it might fit that Frederick was born near 1790 as well which fits with your 1786 BD.
I would be VERY interested if you find out more either to rule this out or in as your connection, and would love to know more about the descendants of Mortimer Gulledge.