Wiki Wanderings: Presidential Grandchildren

You may know that John Tyler, the tenth president of the United States (in office 1841-1845, lived 1791-1862) has two grandsons who are alive as of this writing, making him the earliest president (by some distance) to have living grandchildren. So obviously the question comes to mind, does he have any close competition in this category, and/or what has become of other presidential grandchildren.

Well, Grover Cleveland's granddaughter Philippa Foot invented the trolley problem.