Watch the heartwarming moment Keith Urban stops his show to meet six-year-old fan born with brain condition

Keith Urban gave a young fan the surprise of a lifetime this week ...

While performing in Peoria, Illinois, the Kiwi musician stopped his show after spotting a six-year-old boy sitting atop his dad's shoulders.

In chatting with the boy's parents, Whitney Donaldson and Chase Hammock, the 53-year-old country music star learned that when Kellen was born, "they said he would never walk or talk, and now he knows all your songs."

During the sweet moment - which was captured on video - Urban gave Kellen a fist bump, before signing a cardboard cutout guitar the boy brought to the show.

The pair then shared a hug together.

Posting the footage on Instagram, Donaldson wrote that the moment will be a memory "that will last a lifetime."

Kellen has Hydrocephalus, which results in a buildup of fluid in the cavities of the brain.

He reportedly endured two surgeries by the age of eight days old, and his parents were told he would never "walk, talk or lift his head."

He defied those odds, however, and now Donaldson says he's a music lover who is "completely enamoured" with Urban.