The 41-year-old Guardians of the Galaxy star and the author and eldest daughter of Arnold Schwarzenegger and Maria Shriver welcomed their first child, daughter Lyla Maria Schwarzenegger Pratt, in August. On Sunday, Dec. 13, Chris posted on Instagram a collage of photos of Katherine as a birthday tribute.
One of the pics shows her holding their now-4-month-old daughter, who is wearing a pink outfit and whose face is covered by a Santa Claus graphic, to which a fan joked, "Your baby looks a lot like Santa Claus."
"Happy Birthday Sweetie!" Chris wrote. "You have brought so much light into my life. I'm so glad to be home with you and Lyla."
The actor, who also has an 8-year-old son from his previous marriage to Anna Faris, continued, "You're a great mom, a great step-mom, a great wife, daughter, sister and friend. The world is brighter with you in it. I am one lucky man. Thank you for the love, support and partnership. I love you."
Katherine commented in response, "Awww I love you."
Chris and Katherine have yet to show their daughter's face on social media. Until Sunday, Chris and Katherine had only shared one photo of Lyla on Instagram, a closeup pic of the pair holding the baby's tiny hand, which served as their birth announcement.
Chris' birthday tribute to Katherine also included two never-before-seen photos of his wife when she was visibly pregnant with Lyla.
The birthday girl commemorated her own special day as a first-time mom with a message of gratitude on social media. "31! Feel beyond blessed to be alive, to have my health, my family, my loved ones close, to have spent the day with my daughter and husband, the morning with my family on a walk and to feel so loved, from a safe distance," she wrote on Instagram. "I have a whole new outlook on birthdays after giving birth this year, so today I toast my parents for creating me and my mama for birthing me! I'm so grateful for both of you, your love and our family. I'm also grateful I grew up to marry a man who woke me up with this happy birthday latte he made. I love him so!"
On Friday, the Maverick and Me author shared a photo of a Santa-shaped ornament on a Christmas tree, writing, "While this Holiday season will look different for us all, this little ornament my sister Christina got us, and the experience of our daughters first Christmas is a big silver lining of joy and light for me."
"2020 has been a crazy year, it's not what any of us expected; it's been filled with a lot of challenging times and unpredictable twists and turns," she continued. "It has also been a year of immense joy for those of us who have welcomed life into the world. Being pregnant in a pandemic and having a baby too, was not how I expected my pregnancy and becoming a mother to go, but i couldn't be more thrilled and grateful to have my little Lyla Maria in my life and to be able to be her mom."
Katherine added, "Shout out to all the people who had babies this year, became pregnant, are pregnant, or are trying to get pregnant. It's a wild time to embark on this journey of motherhood and I see you!"