Reiss Gabriel and his two brothers — Ralston and Ricky — were all convicted of possessing a firearm with intent to endanger life.
Police found their DNA on a pistol that officers recovered alongside an Uzi sub-machine gun when they stopped a taxi in April 2017.
At Blackfriars Crown Court on Friday (September 6), Reiss Gabriel was given an 18-year jail term and his brother 14 years each.
Temporary Detective Chief Inspector Driss Hayoukane, from the Metropolitan Police, said: “I am proud of the dedication my officers, notably DS Nick Harvey and DC Irfan Khalifa, showed in tracking down and linking the Gabriel triplets to this case.
“The trio tried to exploit their identical DNA and appearance to try and evade the consequences of their actions, but the hard work of the investigation team prevented their attempts.
“Through their actions in this case these men have thrown away promising careers and futures.
“As the judge stated at sentencing, these weapons were destined to be used by dangerous criminals. This case should send a clear message to anyone considering possessing or attempting to obtain a firearm that we will identify you and bring you before the courts.”
The brothers are the final three of eight individuals charged in relation to this case.