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Hugh Hefner's son, Marston Hefner, pleaded no contest to a misdemeanor domestic violence charge for an incident involving his girlfriend, Claire Sinclair, the 2011 Playmate of the Year.

The 21-year-old Playboy scion pleaded no contest Tuesday to corporal injury to a spouse or cohabitant and is expected to undergo a year of domestic violence counseling, Pasadena City assistant prosecutor Chris Blankenhorn told City News Service. He has also been ordered to stay away from Sinclair for three years.

Marston Hefner was arrested last month after police were called to the Pasadena apartment he shared with 20-year-old Sinclair. Sinclair, a Bettie Page look-alike, had minor injuries and sought a restraining order against Hefner the next day.

Posing for TMZ.com, she revealed a giant purple bruise on her arm and claimed the heir had been violent before.

The playmate told ABCNews.com that she would not press charges if Hefner issued an apology. "I'm looking forward to a public apology," Sinclair told ABCNews.com last month. "I am against any sort of domestic violence so once that's done, I'm ready to bury this and leave it in my past."

"If they care about each other, they'll patch it up," Hugh Hefner told People magazine.

But Sinclair moved out shortly after the incident.

"I don't want any problems moving forward," Sinclair told ABCNews.com. "I need to be completely distanced."

The couple had been dating on and off since August 2010. They haven't spoken since the alleged altercation, Sinclair said, and she doesn't plan on doing so.

"I can only hope Marston gets psychiatric help and seeks medicine for his anger," Sinclair said.

Blankenhorn told the New York Daily News that Hefner can withdraw his plea at the end of three years, similar to an expungement, if he stays out of trouble.

Hefner was also charged with one count of vandalizing a laptop computer after the Feb. 12 incident.

"The (vandalism) charge was dismissed with a waiver, he'll pay restitution for replacing that," Blankenhorn told the Daily News.