Chris Brown snuggled up to Rihanna in the front row at the Grammy Awards last night. The 23-year-old singer hugged and leaned lovingly against his on/off girlfriend - who he is still on probation for brutally assaulting in 2009 - at the ceremony at Los Angeles' Staples Center, and the brunette beauty sparked online speculation the couple are to marry. Rihanna appeared to be wearing a diamond "engagement ring" as she took to the stage at the prestigious awards, and several people took to Twitter to express their surprise at the 'Diamonds' hitmaker's band. One fan wrote: "Rihanna is wearing a diamond on her left ring finger. Really?" Another tweeted: "Rihanna engaged?!?! Or that's some type of promise ring?" While the 'Beautiful People' hitmaker left the ceremony empty handed, Rihanna, 24, picked up the Best Short Form Music Video prize for her hit 'We Found Love' featuring Calvin Harris. Chris was lucky to attend the event at all after he was involved in a car crash on Saturday when his vehicle hit a wall, and while he escaped unscathed, the Bajan beauty is said to have been worried about him.