Mumbai, Sep 13 : Actors Ajay Devgn and Kajol's son, Yug Devgn just marked his 13th birthday which made the star couple feel like they were on top of the moon. To celebrate his special day, both the stars took to their social media accounts and penned heartfelt notes wishing their little boy. Kajol shared a happy selfie with her son, where she hugged him, while Ajay Devgn shared a picture of Yug sitting on his lap while he was comfortably sitting with his legs stretched out against a wall. Kajol, who was top of the world for her son's birthday, wrote on Instagram: 'Happy happy 13th birthday baby boy. This day will never come again in ur life. It's momentous for the both of us.. u because u become a young adult and me because I now have a young adult as a child (sic).' In addition, the actress shared a picture of the cake that was cut into pieces during his birthday ceremony. Captioning her post, she wrote: 'Love you to bits and pieces' Ajay Devgn, expressing his great happiness on seeing his son grow, wrote: 'He's outgrowing my lap already. Happy birthday beta... thoda ahiste ahiste bada ho yaar (Grow up a bit more slowly).' Meanwhile, Yug's aunt, actress Tanishaa Mukerji who is the younger sister of Kajol; shared a special video for him, featuring throwback photos and video clippings of the birthday boy. She captioned her post, "Happy birthday my jaan! Yuggy! You are my child of the sky! Happy 13th birthday my beautiful angel boy! Keep shining." Kajol and Ajay last appeared together on the big screen with the Om Raut directorial 'Tanhaji: The Usung Warrior', where both their performances garnered them much acclaim. Currently on the work front, Ajay Devgn who was last seen in the film 'Bholaa', will next be seen in 'Singham Again', 'Auron Mein Kahan Dum Tha' and 'Maidaan' along with an untitled remake of the Gujarati film 'Vash'. Kajol, who was last seen in the Netflix film 'Lust Stories 2', will be seen in 'Sarzameen' and 'Do Patti'. /IANS