Camila Alves' son Livingston is growing up fast.

The Brazilian model, 40, took to Instagram over the weekend to share a post celebrating her and husband Matthew McConaughey's youngest child's 10th birthday, which occurred last month.

"Nothing fancy…just us…December 28th it was Livingston's birthday!!!" she wrote, sharing a rare photo of Livingston in which he's blowing the candles out on his ice cream cake.

"May your heart, my son, keep its simplicity as you grow in this complicated world!!" she continued. "You challenge me and teach me daily for that I am grateful! What a blessing you are!"

In addition to Livingston, Alves and McConaughey, 53, share son Levi, 14, and daughter Vida, 13. The couple married in June 2012.