The Vital Records of Nantucket don't show any entries for children of Abishai because they removed from the Island on 26 Oct 1778 (Starbuck, p. 693) the same year they were married on 1 Jan. The DOB I have for Frederick Worth is 1800, so that must have been in New York, and that is where you will need to search for other children. There may well be a daughter Hephzibah as that was Abishai's mother's name, but it is unlikely that she was born in Nantucket. Again, she is not shown in the Vital Records. The records do show nine siblings for Abishai's father Benjamin.