Their victim was working at the Balti Hut in Queens Road, Hastings, East Sussex, after he entered the UK as an unaccompanied asylum seeker from Sudan.
He was attacked after he threatened to leave and report his employers to the government, Sussex Police said.
Mominur, Ridwanur and Shahnur Rahman, and their father Siddiqur Rahman were all convicted at Lewes Crown Court.
The victim, who was 18 years old at the time, had been subjected to an unprovoked and prolonged attack, Sussex Police said.
They said: “The victim had been chased from the takeaway through the town centre towards Hastings railway station by Mominur Rahman, who repeatedly hit him with a metal bar.
“Once at the railway station, he was further assaulted by both Mominur Rahman and his brother Shahnur Rahman.”
Police said the pair had repeatedly hit, kicked and stamped on the teenager.
“A short time later, a third brother – Ridwanur Rahman – arrived and punched the victim to the head while being held down by Shahnur Rahman,” police said.
“The brothers’ father Siddiqur Rahman then travelled to join them at the station and he also repeatedly stamped on the teenager’s head.”
The attack only stopped after railway staff intervened, police said.
Mominur Rahman, 23, was sentenced to 53 months in prison for attempted GBH with intent, and possession of an offensive weapon.
Ridwanur Rahman, 29, was jailed for 45 months for attempted GBH.
Shahnur Rahman, 31, was sentenced to 48 months imprisonment for attempted GBH.
Siddiqur Rahman, 57, was given an 18 month prison sentence, suspended for 18 months, for affray.
The four men, all of Horntye Road, St Leonards, were convicted at the end of a trial at Lewes Crown Court and sentenced on Wednesday.