Diane Keaton’s son, Duke, is grieving his late mom. The 25-year-old was seen in public for the first time since the legendary actress died at age 79 on Saturday. Duke was photographed leaving Diane’s Los Angeles home on Sunday, wearing all black and carrying a backpack on his shoulders. He subtly honored the “ First Wives Club” icon by wearing two silver cross necklaces, paying tribute to Diane’s signature “devoted nun” style. The look, which she introduced in the 1990s, involved wearing