The Narula brothers - Achin, 24, and Sarthak, 23, - won the mega amount on the 'Jodi Special' episode of the eighth season of the show, hosted by megastar Amitabh Bachchan.
"This was unexpected and it is totally unbelievable. We had thought we will win about Rs.25 lakh and then we will leave. But this has turned out to be a life-defining moment for us," Achin, who is into marketing, told IANS.
His brother Sarthak is a student.
According to a source from the set, the duo was extremely positive and calm on the 'Hot Seat' and answered questions with confidence and ease.
"I knew the answers to the last two questions," Achin said, adding that the bigger challenge was sitting in front of a personality like Big B.
"The atmosphere on the set with Bachchan, the audience, the music...it all adds up to the thrill," he said.
Now how will they spend such a big amount?
"One can't plan these things. It's a huge amount and we will definitely spend it wisely," said Achin, whose family went through financial losses and had to sell off their house to pay debts, six years ago.
The makers of KBC are ecstatic about the "momentous occasion".
"Over the years, the show has evolved from being just a knowledge-based game show to something which is greatly appreciated and aspirational to our audience. We hope KBC continues to inspire people the way it has been all these years," Gaurav Seth, senior vice president, marketing, Sony Entertainment Television, said in a statement.
Siddharth Basu, chairman and managing director, Big Synergy Media Ltd., which produced the show, said: "We have been waiting for a moment like this since the inception of this show. It is a pleasure to see bright brains like Achin and Sarthak battle it out for the 'Maha Jackpot'."
"It will be our endeavour to continue to raise the bar on this knowledge-based game show so that we can encourage more and more people to achieve their dreams through this show."
The episode in which the duo won was shot in Mumbai Friday evening.