Likely Frederick Coleman, one of Eliza's younger brothers. Little further is known of him.

There is a slight possibility that this is Frederick Coffin, the brother of Elizabeth Coleman (Eliza's mother) and of Phebe Collins, aged ca.31 (b. in 1784--never married). However, it is not known if he even was living in the Dartmouth area; it is possible he returned to Nantucket. And the fact that Louisa refers to Eliza's escort as simply "Frederick" rather than "Uncle Frederick" or "Uncle Coffin" (for he would be her uncle as well as Eliza's) suggests this is not their uncle.