AceShowbiz - Chris Hemsworth is celebrating Liam Hemsworth's 31st birthday in a sweet way. Offering a loving tribute to his younger brother on social media to commemorate the latter's milestone, the "Thor" actor unleashed a childhood photo of them together.

On Wednesday, January 13, the 37-year-old treated his 42.2 million Instagram followers to a picture that saw his younger brother sitting on his lap as they both smiled for the camera. The snap saw the two wearing what appeared to be matching school uniforms and black shorts as they were joined by their dog.

In the image, Chris could be seen rocking the '90s looking curtain haircut, while his younger sibling beamed next to him. In the caption, he quipped, "Happy birthday @liamhemsworth this photo was taken 3 years ago today, damn time flies but you haven't changed a bit."

Chris' post was met with positive comments from his famous friends. One in particular was Australian boxer John Wayne Parr who wrote, "Back when Thor was a little fella." Actress Isla Fisher of "Confessions of a Shopaholic" gushed, "That's too cute." Adventurer Bear Grylls additionally raved, "Classic photo.... and you're still best buddies it seems - that's the key bit.

Liam himself took to his own Instagram page to thank those who sent him birthday wishes. Sharing a black-and-white picture of him in the pool as he raised his hands, he penned, "Here's to a better year than the last! Cheers for the birthday wishes!"

A little over two months earlier, Liam commemorated his brother Luke Hemsworth's 40th birthday. Offering tribute for the "Westworld" star on Instagram, he noted, "Happy 40th birthday @hemsworthluke ! You've been a wonderful brother all these years. I've taught you well...the rest is up to u. Love ya Luke!"

"The Hunger Games" star and his family also threw a 1920-themed birthday party for Luke. In the celebration, he invited his girlfriend Gabriella Brooks who joined his parents, his brothers as well as their wives Samantha and Elsa Pataky.