There seems to be a lot of confusion about these two Benjamin HATHAWAYs and I refer folks to the "Hathaways of America" books (see Hathaway Family Association).
Abraham HATHAWAY (1652 - 1725 MA) m. Rebecca WILBORE and had sons:
Abraham (1685 - 1754) m. Sarah CHACE/CHASE. They had son Benjamin (1724) who m. Hannah BAYLES/BAILEY.
Benjamin (1699 MA - 1762 NJ) m. perhaps CLEMONS. They had son Benjamin (1722) who m. Mary FAIRCHILD.
The two younger Benjamins were both grandchildren of Abraham and Rebecca and were first cousins.
(I've yet to decisively research a [younger] Benjamin HATHAWAY marriage to Hannah HOPKINS, but) I hope the above might help other researchers.
Comments and corrections appreciated.