Shivam was killed when the truck hit the motorcycle on Jaunpur-Mirzapur road late last evening, they said.
His uncle Govind Mishra (35) and another rider Kamlesh Mishra (30) were injured in the accident and were rushed to the district hospital.
They were referred to Varanasi today, police said.
The truck driver was nabbed by the local residents and handed over to the police.