None of them are in my kitchen. 
But no, seriously: TIL (or, more precisely, figured out) that they are the only three U.S. presidents to serve two full, consecutive* terms in office without a census occurring during their presidency.
Before you ask “So?”, please recall this is MPSIMS! 
*Grover Cleveland managed the same feat in non-consecutive terms.
Right, as an artifact of being the only three who have served two full consecutive terms after being first elected in a “zero” year election.
Indeed. 
What do these presidents have in common:
John Adams
Hiram U. Grant
Theodore Roosevelt
Herbert Hoover
Richard M. Nixon
Wow, I dunno. Can you give us a hint?
George Washington is excluded from the list because the answer involves only part of a term.
Just checked to see if the answer was “they are all dead”, but not yet.
They’ve never been in my kitchen.
Ok, too difficult, I guess.
Grant: 582 days
Nixon: 549 days
Adams: 380 days
TR: 233 days
Hoover: 54 days
represents the remainder of the term after the last living ex-president died. Each of these presidents became the only living ex-president upon leaving office, with Hoover being the longest sole ex-president, for just shy of 20 years.
Okay, I’ll play.
What do these Presidents have in common?
Andrew Jackson
Zachary Taylor
James Buchanan
Andrew Johnson
Chester Arthur
Benjamin Harrison
William Taft
Woodrow Wilson
Lyndon Johnson
Ronald Reagan
George W. Bush
Donald Trump
People questioned their qualifications to be President? Works for: Trump, Bush, Regan, and probably LBJ. Not sure if it continues to work.
Ok, I’ll play too…
None of them have ever been in my kitchen.
It’s true about Buchanan and Johnson. Benjamin Harrison also lost the popular vote. But so did Rutherford Hayes. He should probably be on the list, if that’s the answer.
Maybe it was that someone in a very specific and citable way questioned their cognitive abilities. There was a lot of speculation that Bush had dyslexia, and I read one fairly well-reasoned article in a prominent newspaper, although it was a paper paper, and I can’t find it online now. Wilson actually was incapacitated, and it’s been speculated that his wife ran the country for several months after he had a stroke-- it’s certain he wasn’t doing it. Reagan was diagnosed with Alzheimer’s so shortly after his second term, that it’s hard to imagine he wasn’t somewhat incapacitated during his last year or two. And the APA is considering revising its rule about diagnosing public figures whom doctors have not met personally so that they can comment on Trump’s mental health.
IIRC, there was a lot of rumbling about Buchanan being a little more than eccentric, but my memory is shaky here.
Johnson, I recently heard, had some pretty frightening paranoia during the end of his term, and some people close to him were talking 25th amendment. I think a book detailing it just came out.
On the other hand, I can’t remember hearing anything about Taft, and he was appointed to the Supreme Court after he was president.
Oh, well, in that case, I didn’t vote for any of them.
All of them were older than the President they succeeded.
Here’s one ( though this could change):
Andrew Jackson
James Polk
Donald Trump
What do
John Adams
Thomas Jefferson
John Q Adams
Martin Van Buren
William Henry Harrison
Zachery Taylor
Millard Fillimore
James Garfield
Donald Trump (for now)
…
Have in common.