Yes, Benjamin was the son. He 'married' Sloane Jane Tully and they had eight children. I have not found their marriage, which should be about 1855. Sloane's father was Assistant Harbour Master at Launceston.
I have also not found Benjamin's birth, which I was expecting to be 1829. John and Isabella's marriage in Liverpool in 1831 seems a bit 'late'. However, John is named a mariner in the banns; that might account for him becoming a pilot in Tasmania.