Former first lady Barbara Bush was hospitalized on Tuesday for a respiratory problem. Her husband, George H.W. Bush, decided to tweet about how she's apparently feeling better, especially after some nice well-wishes from former and current presidents. That's where the trouble begins: 

You see, there are multiple living former presidents missing from this tweet. So which one did George H.W. Bush just subwteet?

 Barbara's son, George W. Bush. Odds: 30 to 1. 

This is the most obvious omission from the list. Sandwiched by two presidents who did have the good sense to call or tweet about Barbara, the former first lady's own son might be the subject of one of the top five subtweets of all time (OF ALL TIME). That's quite an accomplishment, as the elder former president Bush only joined Twitter about a month ago. We don't think it's particularly likely that H.W. subtweeted his own son in this instance, but this seems to be quite a popular interpretation: 

Former President Jimmy Carter. Odds: 45 to 1. 

Carter doesn't seem to have quite have the same relationship to the Bushes that former Democratic president Bill Clinton does, though it's technically possible that H.W.'s omission here is supposed to refer to Carter. That is also a somewhat popular interpretation on Twitter, especially for those leaning right of center

None of the Above: His own wife, Barbara Bush. Odds: 3 to 1. 

AP

Bush the Elder's tweet is definitely a joke at someone's expense, and we think it's most likely that the former president was poking fun at his own wife (and himself). Both presidential subtweet interpretations above assume that the emphasis should be on the first part of Bush's tweet: "Barbara thanks @BarackObama & @billclinton for their get-well wishes." But we think the emphasis goes on the latter part: "and is heeding their advice." As you might have heard, Barbara Bush is a little bit strong willed. H.W. was probably referring to the fact that Barbara isn't always keen on listening to advice from her husband, despite his excellent taste in socks. But she took the advice of Clinton and Obama, which was to get well. Ha ha. Joke (probably!) explained, you're welcome.