Ian Somerhalder, one of the favorites to play Christian Grey in the Fifty Shades of Grey movie, has hinted that his ex-girlfriend Nina Dobrev was to blame for their recent split. The couple called it quits after several years together, with sources confirming the news to People magazine.

The pair were only spotted together in April, taking their cat to the vet late at night. Somerhalder, 34 and Dobrev, 24, kept their romance secret during the early days as a couple, mainly because they were co-stars on the hit CW show Vampire Diaries. "I didn't want to be dating one of my costars," Dobrev told Seventeen last fall. "My goal on the show was to be professional. But sometimes you can't help who you have a connection with, and you can only fight it for so long - which I did for a really, really long time."

Though no reason has been given for the split, Somerhalder hinted that it was Dobrev who ended the relationship in a Twitter post this week. Quoting playwright Lillian Hellman, the actor told followers, "A THOUGHT FOR TODAY: People change and forget to tell each other."

A source told Us Weekly that the pair will "continue to work together and remain best friends, which is where the relationship started." Both stars are reportedly planning to stay "consummate professionals," as they continue to work on the Vampire Diaries.

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