Love knows no age barriers - and "Playboy" chief Hugh Hefner proves this. The 84-year-old has apparently got engaged to his 24-year-old girlfriend Crystal Harris.Hefner posted on Twitter that he has gifted Harris a ring on Christmas eve, the tmz.com reports."After the movie (The Tourist) tonight (Dec 24), Crystal and I exchanged gifts. I gave Crystal a ring. A truly memorable Christmas Eve," he posted.Hefner has married twice before. He first tied the knot with Mildred Williams, the marriage lasted from 1949 to 1959, and later with model-actress Kimberly Conrad with whom he split earlier this year.
