Brown was convicted of assaulting Rihanna in 2009 but they resumed their relationship in 2012 before splitting a few months later.
The Kiss Kiss hitmaker has been in rehab since last year (13) after he was ordered to complete 90 days of anger management treatment relating to his ongoing legal woes, but Brown reportedly started texting his ex-girlfriend on her birthday (20Feb14).
A source tells New York Post gossip column Page Six, "Chris started texting Rihanna on her birthday, and the two have been sending each other a flurry of texts ever since. Rihanna didn't write back right away... but later that night she started getting sentimental and texted back... Since then, the two haven't stopped texting each other and friends are freaked out that she's going to start dating him again."
The Umbrella singer was spotted getting close to another ex-boyfriend this week (beg24Feb14) when she duetted with rapper Drake onstage in Paris, France.