Johnny Galecki Sends Birthday Love to 'Fake Wife' Kaley Cuoco After Splitting From Girlfriend

Johnny Galecki is sending love to former Big Bang Theory co-star and ex-girlfriend Kaley Cuoco as she celebrates her 35th birthday. The actor, 45, had nothing but sweet words for his close friend and "fake wife" as he weathers a reported split from girlfriend Alaina Meyer, with whom he welcomed son Avery almost a year ago.

"The happiest 74th birthday to my fake wife [Kaley Cuoco]," he captioned a series of photos of the two together over the years. "You know how much I adore you and respect you. I'm so proud of all you are doing and so happy with your happiness. But most of all, our friendship and partnership over the years. XO, dear. Congratulations on 82 years of age."

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The Flight Attendant actress responded to the cheeky birthday wishes, "THIS IS EVERYTHING! I LOVE U MOOKS! Even at my old age of 82!" Cuoco and Galecki privately dated while filming their hit CBS sitcom from 2007 to 2009. Even after breaking up, the two remained close as they eventually played a married couple on the long-running show, which wrapped up in May 2019.

"We dated really early on for almost two years. When we did the pilot, I was crushing so hard on Galecki, but he had a girlfriend," Cuoco said of their relationship on Dax Shepard's Armchair Expert podcast last month. "We got together and just fell mad for each other for two years, but then we broke up. Luckily, Johnny and I came out of it so brilliantly, and we're closer today than we ever were."

The 8 Simple Rules star would go on to marry husband Karl Cook in 2018, while Galecki found love with Meyer, 23, in September 2018. In November 2019, the couple welcomed son Avery. "With full and grateful hearts we welcome our beautiful Avery into this incredible world," Galecki wrote on Instagram at the time. "Thank you for all of your love and support."

Monday, a source confirmed to PEOPLE that Meyer and Galecki had split and were focusing on co-parenting Avery. Last week, Meyer took to Instagram to reflect on the "gnarliest year" of her life "with the highest highs and the lowest lows." She continued, "There was a healthy baby boy that needed me and kept me grounded and centered. It's absolutely insane how time flies, watching this little one come into himself is the best gift. I am so grateful for his health and our journey together."