his paternal grandparents were merchant george hawkes and ann (née lawrence) hawkes. his maternal grandparents were merchant william jehiel forbes and charlotte antoinette (née root) forbes, the daughter of joel root, an early entrepreneur and supercargo on the sealing ship "huron". his grandmother charlotte's sister, susan huldah forbes, was married to benjamin silliman jr., the maternal grandfather of hawkes' wife alice silliman belknap.