Chris Brown wishes Rihanna a Happy Birthday

By Arienne Thompson, USA TODAY

Posted February 20, 2012

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Rihanna seen leaving her hotel on Feb. 20, her 24th birthday, in London. (Credit: By Alex Moss, FilmMagic)

Speculation about a possible reconciliation between pop stars Chris Brown and Rihanna has been swirling for months now. But, there seems to be one telltale sign that they're, at the very least, in communication.

Brown tweeted a message to Rihanna, who turns 24 today. "HAPPY BIRTHDAY ROBYN!" he wrote, using the singer's real first name. She tweeted back a simple "Thanks!" in response to his well wishes.

Their friendly banter doesn't stop at Twitter, however. Rihanna also enlisted Brown to appear on her upcoming single Birthday Cake, a move that the song's producer told MTV would "shock the world."

Brown, who staged a comeback at this year's Grammys, has not been so nice to everyone on Twitter, though. He snapped back at critics who were not happy about his double performance and win during the show.

Brown and Rihanna infamously split when he savagely beat her the night before the Grammys in 2009. Brown eventually pleaded guilty to felony assault and was sentenced to probation, counseling and community service.