Instagram of the Day: George W. Bush Calls Bill Clinton ‘Brother From Another Mother’

This is what happens when former presidents discover hashtags.

Bill Clinton Tweeted a thank you to George W. Bush Wedesday for receiving a copy of his new book, "41," with the hashtag: HowAreYouSTILLNotOnTwitter.

Then Bush replied with an Instagram, screenshotting Clinton's tweet and adding his own special hashtag in the comments: BrotherFromAnotherMother.

Still waiting on Obama's response via Vine.