Answer:
Samuel Adams and John Adams were second cousins which means they had the same great-grandfather and grand-mother.
Their fathers, Samuel, Sr. (1689-1748), and John, Sr. (1691-1761), respectively, were first cousins.
Their paternal grandfathers were brothers John Adams (1661-1702) and Joseph Adams (1654-1737), respectively.
Their shared great grandparents were Joseph Adams (1626-1694) and Abigail Baxter (1634-1692).