Carrie Underwood Shares Photos from Son Jacob's 4th Birthday Celebration: 'My Sunshine'

Carrie Underwood can't believe how fast her youngest is growing up!

On Sunday, the country singer, 40, shared a sweet tribute in honor of son Jacob's 4th birthday, featuring some photos from the little boy's Spiderman-themed celebration.

"This was yesterday…and now you are 4.😩," Underwood wrote alongside a photo of Jacob as a baby. "Happy birthday, sweet Jake…my sunshine!!! God truly blessed us when he gave us the miracle of you!!! We love you! ❤️❤️❤️ Thanks, @iveycakestore for the adorable and delicious cake! You guys are the best! 🥳🎉🎈."

Jacob's birthday party featured a blue and red two-tiered cake decorated with Spiderman webbing and a night skyline as well as a Spiderman action figure sitting atop the dessert. The little boy's name was also written at the base of the treat and the number 4 was iced on the cake in yellow.

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Along with Jacob, Underwood and husband Mike Fisher are also parents to 7-year-old son Isaiah.

Earlier this month, the "Before He Cheats" artist shared an adorable video on Instagram of Jacob "starting the day off right" with an energetic workout.

"The boys found one of my old Tae Bo DVDs in a box of things and Jake thought he'd have himself a little morning workout! 😂," the mom of two captioned the video. "I may soon have myself a gym buddy! 💪💪💪."

The preschooler could be seen enthusiastically trying to keep up with the Billy Blanks-led workout video in a white t-shirt and red sweatpants as his mom, recording from behind him, laughed at the sight.

Underwood and her family also recently enjoyed a fun-filled outing at the NASA Space Center in Houston, Texas.

"Had the best day @nasa talking to astronauts in space, driving moon rovers, checking out space station replicas and meeting some really cool people!" Underwood wrote on Instagram earlier this month.

"Thanks to @astro_kimbrough and everyone there for showing us around and being so sweet to my boys (who may just end up being future astronauts)!!! #Houston #Space #BeamMeUp," she added.