People.com Celebrity Parents Hilary Duff Celebrates Son Luca's 9th Birthday: He 'Taught Me that My Heart Can Keep Growing Bigger' Hilary Duff, who shares daughter Banks with husband Matthew Koma, is expecting her third child By Karen Mizoguchi Published on March 21, 2021 12:15 PM Share Tweet Pin Email Hilary Duff with son Luca and husband Matthew Koma. Photo: Hilary Duff/instagram Happy birthday, Luca! On Saturday, Hilary Duff celebrated her son turning 9 years old with a small party at her home. "9???? How? You know it's been a big day when there has been zero posting …nor did I have time to make a video with memories from our past year with whatever stock music Instagram won't flag me for," Duff, 33, wrote on Instagram, along with a photo of some festive balloon decorations from the bash. "Luca provided me with the best 9 years of my life and taught me that my heart can just keep growing bigger and bigger and that it's truly endless," the Younger actress wrote of her eldest child, whom she shares with ex-husband Mike Comrie. The star and husband Matthew Koma, who share 2-year-old daughter Banks, are also expecting their second child. "Was so happy to celebrate this year in a (safe) more normal way and make this dude feel extra special! Next year I will get back to photo collaging," added Duff. "I desperately didn't want to have a baby on his birthday so he could keep his day all to himself. ….. success. Now please please body let do this." Want to get the biggest stories from PEOPLE every weekday? Subscribe to our new podcast, PEOPLE Every Day, to get the essential celebrity, entertainment and human interest news stories Monday through Friday. Also on Saturday, Koma shared a birthday tribute to Luca, along with a series of photos of the young boy. "It's my little dude's 9th birthday tomorrow and he asked me to put Green Day on in the car last week. Old Green Day. Makes me tear up," the songwriter wrote on Instagram. Duff's sister Haylie also wished her nephew a happy birthday. "We just love you to bits Luca! Happy 9th Birthday bud!" she shared on Instagram, along with a photo of her daughter Ryan posing with Luca. The Sweetest Photos of Hilary Duff and Matthew Koma's Growing Family Recently, Duff opened up about her pregnancy and her prediction that she will have another boy. On a new episode of Informed Pregnancy Podcast with Dr. Elliot Berlin, Duff spoke about her blue hair color, joking, "I know the blue hair seems like we do know, but we really don't," and later adding, "I'm actually a little scared to have another girl because Banks was a tough — she was a tough cookie as a baby, but she's so great now, so I could see it. But then I don't know, in my mind I'm like, 'Maybe she's my only little princess and she's going to have her rough-and-tumble brothers.' " The soon-to-be mom of three added, "Either way, we're stoked and super excited. Everyone that's close to me thinks boy, and then everyone that's more of a stranger that's like, 'What are you having?' they're like, 'We call girl.' "