OMG! They grow up so fast! On Sunday, Chris Pratt's son Jack hit a major milestone - he turned 13! Officially a teenager! Can you believe it?! And yes, you can bet his dad is freaking out! The Guardians of the Galaxy actor took to his Instagram Story over the weekend to celebrate the big birthday by sharing a ton of rare photos of his son, writing: "I have a teenager??? Jack, I can't believe you are 13 today. I've watched you grow into such an incredible young man, and am truly proud of the person you are becoming.