Toward the end of the Nixon presidency, there were no living former presidents.
THANK YOU!
"When I was a pup, we got spanked by Presidents till the cows came home. Grover Cleveland spanked me on two non-consecutive occasions,"
There have three occasions where we have had 5 living former presidents at the same time:
Under Clinton: Nixon, Ford, Carter, Reagan, and Bush, Sr.
Under George W. Bush: Clinton, Bush, Sr., Reagan, Carter, Ford
and under Lincoln: Buchanan, Pierce, Filmore, Van Buren, and Tyler.