She's a ''Titanic'' star, and he's the Oscar-winning director of ''American Beauty,'' but Kate Winslet and Sam Mendes have managed to keep a low profile. They kept their Caribbean wedding in May a secret to everyone, including their families, and they kept mum on the Dec. 22 birth of their son, at an undisclosed New York hospital, for four days. Their publicist announced the arrival of little Joe (7 pounds, 3 ounces) on Friday with a pithy statement: ''The couple is overjoyed.''
It's the first child for the 28-year-old actress and the38-year-old ''Road to Perdition'' director. Winslet, who'll be seen early next year in ''Eternal Sunshine of the Spotless Mind'' with Jim Carrey, also has a three-year-old daughter. Little Mia's father is Winslet's ex-husband Jim Threapleton, who, like Mendes, is a British director.