According to merchant banking sources, the Jhunjhunwalas together bought 25 lakh scrips of SpiceJet through open market transactions.
The shares were purchased on an average price of Rs 38.94 apiece, valuing the transaction at Rs 9.73 crore, they added.
However, identity of sellers could not be ascertained.
In July last year, Rakesh Jhunjhunwala's Rare Enterprises had acquired 25 lakh shares of SpiceJet for Rs 7.69 crore.
Last month, SpiceJet's promoter Kalanithi Maran had increased his stake in the no-frills airline from 16.27 per cent to 22.05 per cent on account of allotment of equity shares following conversion of convertible debentures.
The company had allotted 35,931,453 equity shares to Mr Maran following conversion of 13 million unsecured compulsorily convertible debentures for an aggregate value of Rs 130 crore.
The overall holding of promoters in the airline also climbed to 52.14 percent from 48.59 per cent at the end of March quarter.
The airline currently operates more than 350 daily flights to over 50 Indian cities and eight international destinations.
Shares in SpiceJet, on Friday, surged by 6.44 per cent to close at Rs 40.50 apiece on the BSE.