The photo was taken by Aundrea and Matthew Smith at a pre-K graduation in Fairfield County, Connecticut.
The Smiths shared the photo on Instagram saying their son hugged his sister after graduation and told her, "I'm just so proud of you."
At those words, the young girl started crying.
"As we wiped away our tears, my husband asked her, 'Pumpkin, why are you crying?' She responded, 'I'm just so happy,'" the post read.
In just four days, the photo has received nearly 20,000 likes.