Ever since little Luca Cruz Comrie entered the world in 2012, proud mom Hilary Duff hasn't been able to stop sharing adorable photos of him. In honor of his fifth birthday on Sunday, the Younger star posted another sweet snap of her son on Instagram, and the caption contains a touching message. "Hey kid.... the past 5 years have been the BEST, hardest, most blessed years of my life," she writes. "I love you so much. The world is yours my love ...I hope you take it❤️ Happy Birthday Luca Cruz." The difficult times she mentions are likely in reference to her and Luca's father, Mike Comrie, finalizing their divorce. Despite a few bumps in the road, it seems Hilary and Luca have another great year ahead of them.