Rieko, 21, has established himself as a first choice in the All Blacks team since he made his debut in 2016 and is now arguably the world's best winger with 18 tries in 18 tests.
The contract also keeps him with his brother at the Auckland Blues Super Rugby team.
Terms were not disclosed but the New Zealand Herald said Rieko was likely to have joined the upper echelons of New Zealand Rugby's pay scale and earn more than NZ$1 million (503,617 pounds) a year.
"I feel incredibly privileged to get the opportunity to play my rugby here for another four years," he said in a statement.
"I want to give it my best shot at serving the black jersey and, hopefully, I'll get the chance to play at the Rugby World Cup in the future. That's a huge motivator for me."
Both brothers had been the targets of other Super Rugby clubs but Rieko said he was keen to help his home town team out of their long-term slump.
"It was obviously tough this year for the Blues, but I feel we're on the verge of something special and I want to be a part of that journey," he said.
"Auckland is my home, it's where I grew up and it's the city that made me as a rugby player, so I want to do my bit to help it move forward."
Loose forward Akira, 23, has played one match for the All Blacks against a French XV in 2017 but is yet to make his test debut.
His new contract expires in 2021 and he said trying to force his way back into the national side was a major goal.
"I want to keep playing my best rugby and try and make it back into the All Blacks again," he said.
"It will also be special sharing the next few years with my brother and representing our family out on the footy field."
The retention of the duo will be a massive boost for NZR, who are involved in a never-ending battle to keep their top players at home and available for the All Blacks.
Former flyhalf Lima Sopoaga said last week the All Blacks jersey had lost its allure, especially to players from lower socio-economic groups who could earn significantly larger salaries in Europe.
(Reporting by Greg Stutchbury; Editing by Nick Mulvenney)
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