News Hilary Duff's Son Luca Is the Cutest Little Gentleman: See His Kind Act! By Antoinette Bueno 8:02 AM PDT, March 25, 2016 Photo: Getty Images Hilary Duff is raising her son Luca right. On Thursday, the 28-year-old Younger star Instagrammed this super cute moment of her adorable 4-year-old son being a total gentleman. "This was the sweetest moment I caught. Luca trying with all his might to lift a low branch for Leah," Duff captioned a pic of her pal ducking down under a branch. "Little gent #proudmutha" PHOTOS: Stars Share Pics of Their Cute Kids! Luca turned four years old on Sunday, and Duff celebrated her son's special day alongside her ex, former hockey pro Mike Comrie. "We are so proud of this boy!" Duff said of a sweet photo of Luca sandwiched between his parents. "You….are magic my little big boy," she also wrote about a pic of Luca eating birthday cake. "Happy 4th birthday. My heart just explodes for you." Duff and Comrie's divorce was finalized last month. The two were awarded joint custody of their only child together, even though Duff initially asked for primary custody in her February 2015 divorce filing. WATCH: Hilary Duff Adopts Her Late French Bulldog Sister -- Meet Peaches the Puppy! And the single life certainly is agreeing with Hilary. Check out the video below to see the former Disney star showing off her smoking hot bikini bod in Hawaii! Hilary Duff Flaunts Rock Hard Abs in Itsy Bitsy Bikini in Hawaii Related GalleryAdorable Tots: Celebs and their Cute Kids!