The Narula brothers, who hail from Delhi, emerged victorious after answering all the 14 questions correctly with the help of four lifelines.
Achin is a marketing manager and Sarthak is a student. Achin has been trying to be a part of the iconic show for the last 10 years but always fell short of being selected for the fastest finger first contest.
Bachchan, 71, hinted about the big win on his official blog and Twitter handle while posting his pictures from the show.
"The beauty and the excitement of KBC at its very maximum! Just an incredible moment," Bachchan tweeted, followed by a photograph from the sets of the show featuring the winners.
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"Bazuumbaaa," the actor posted along with the snap adorned with the Rupee symbol.
Bachchan, who has been hosting the show for 14 years, was reportedly speechless as the brothers made it to the top prize.
"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."
Gaurav Seth, Senior Vice President Marketing, Sony Entertainment Television called the win a "momentous occasion" while congratulating the brothers on their win.