Who were the presidents that followed in their fathers' footsteps?

Well, I suppose we all know that George W. Bush followed in George H. W. Bush, his father's footsteps to become president. John Adams and John Quincy Adams, the 2nd and 6th presidents. Theodore Roosevelt and Franklin Roosevelt, the 26th and 32nd presidents. I also know that William Harrison and his grandson Benjamin Harrison were the 9th and 23rd presidents of the USA.