CNN —  

Former President Bill Clinton teased his successor via Twitter that he should improve his social media strategy but also let George W. Bush know that he’s reading the book he wrote about his father.

“Received my copy of #41 by #43, George W. Bush. Touching tribute!” Clinton’s Twitter account posted Wednesday.

But Clinton, who’s joked that he’s become so close with the Bushes that people think he’s “the black sheep son” – couldn’t let the moment pass without teasing Bush – in hashtags.

“#HowAreYouSTILLNotOnTwitter #PresidentialTweeters,” his account read.

Bush responded later that night – but via Instagram.

“Thanks, 42! Hope you like the book about your pal, #41. #HowAreYouSTILLNotOnInstagram #PresidentialGrammers #BrotherFromAnotherMother.”