People.com Celebrity Parents Carrie Underwood Celebrates Her Son Isaiah's 6th Birthday: 'You Have the Biggest Heart' Carrie Underwood shares sons Isaiah and Jacob with husband Mike Fisher By People Staff Published on February 27, 2021 06:15 PM Share Tweet Pin Email Photo: Carrie Underwood/Instagram Happy birthday, Isaiah Michael Fisher! On Saturday, Carrie Underwood gave a sweet shout-out to her son, who turned 6. "Today, we celebrate Isaiah… because today, he is 6 whole years old! Isaiah, you are kind, funny, smart, the best big brother, a lover of cuddles and crafts and you have the biggest heart and the best imagination!" the mom of two, 37, wrote on Instagram. "You love to make people feel good and you especially love to make them laugh! God has given you so many gifts and every day, I thank Him that I get to be your mom! I love you, Monkey! ❤️❤️❤️ Happy birthday!" said Underwood, who shares sons Isaiah and Jacob, 2, with husband Mike Fisher. Along with the tribute message, the country star shared photos from Isaiah's Power Ranger-themed party, including the cake which was made by Ivey Cake, a bakery in Tennessee. Want to get the biggest stories from PEOPLE every weekday? Subscribe to our new podcast, PEOPLE Every Day, to get the essential celebrity, entertainment and human interest news stories Monday through Friday. Carrie Underwood Got 'Emotional' Recording Christmas Duet with Son Isaiah: 'I Was Crying' Months before his birthday, Isaiah made a cameo on his mom's Christmas album My Gift, lending his singing voice for their cover of "Little Drummer Boy." "When I first heard it back I was laughing and crying at the same time because it was just this beautiful, pure moment from him," Underwood previously told PEOPLE (the TV show!) of listening to her son's rendition of the song. "He did such a great job. He remembered the lyrics and he sang it with his whole heart." And asked if Isaiah understands that his mom is a famous singer, Underwood said she can "see little lightbulbs coming on." "It's mainly when other people talk about it to him," she explained. "If we'll be there with a little friend and the friend's mom is like, 'Oooh now this is Carrie Underwood.' " In December, the My Gift: A Christmas Special from Carrie Underwood star told PEOPLE that one big silver lining amid the ongoing coronavirus pandemic was being able to spend more time with her family. "I tried my best to start every morning just being thankful. We're all healthy right now," Underwood said at the time. "And we have each other, and I got to just stay in one place, which hasn't happened in a long time and really just watch, especially my youngest one, to get to know him and kind of watch him grow."