Brown shared an image on Monday (December 3) of himself smoking and Rihanna posing in the background while wearing a white bra.
He boasted in a caption accompanying the image: "What would music today sound like if these kids didn't exist?"
Rihanna previously posted an image of herself hugging a man believed to be Brown. The 'Diamonds' singer had two days earlier shared a picture of Brown lying on a bed.
The stars have generated controversy with rumours of a renewed romance, several years after Brown was convicted of assaulting Rihanna.
Brown briefly quit Twitter last week due to a heated exchanged with comedy writer Jenny Johnson over his and Rihanna's relationship.
Listen to Rihanna's 'Nobody's Business' featuring Chris Brown below: