Tom Selleck has been immortalized on the silver screen for decades, but the actor’s marriage to dancer Jillie Mack has proven equally longevous, still going strong after 33 years. After a secret wedding ceremony with Mack in 1987, Selleck left his then-hit TV series “Magnum P.I.” to raise a family the following year. The actor claims that friendship is the key to sustaining a life together. “I get up before Jillie and put on the tea kettle, so when she gets up, her tea water is hot,” Selleck, 76, told Closer Weekly. “I think I’m pretty romantic.” Now, the couple grow avocados and raise horses on their 65-acre ranch in Hidden Valley, California, where they have lived and tended the land for over three decades. “They still love spending time together,” a family friend explained. “They like the simple life.” Selleck’s first marriage to model Jacqueline Ray came to an end in …