The CEO of steel giant ArcelorMittal and a member of one of India’s richest families is investing $1 billion into the William Chisholm-led purchase of the Boston Celtics.

Aditya Mittal will likely be the second-largest stakeholder of the 18-time NBA champions and potentially be the alternate governor in the future, according to multiple people familiar with the details. Chisholm will be the largest shareholder and take over as team governor from Wyc Grousbeck after the 2027-28 season.

In March, Chisholm’s group reached a deal to buy the Celtics in two stages, which was the stated goal of the Celtics’ current ownership, led by the Grousbeck family. The deal values the team at $6.1 billion in the first payment, marking the most expensive control sale in sports team history.

The deal was not fully financed when the sale agreement was reached. The group has spent the last few weeks raising money and determining which of the existing minority owners will remain in the ownership group. Mittal helped close the funding gap.

Mittal is the son of Lakshmi Mittal, who serves as executive chairman of $62 billion-in-revenue ArcelorMittal, the world’s second-largest steel and mining company after China’s state-owned Baowu. Lakshmi started Mittal Steel in the late 1980s and merged the company with France’s Arcelor in 2006. He is worth $23.9 billion, according to Bloomberg.

Lakshmi has been on the board of Goldman Sachs since 2008. Goldman was the financial advisor for the Chisholm group. BDT & MSD and JPMorgan Chase co-led the sale process for the Celtics.

ArcelorMittal and JPMorgan Chase declined to comment. Representatives for BDT and Goldman Sachs did not respond to requests for comment ahead of publication.

Private equity giant Sixth Street was part of Chisholm’s initial group when the agreement was reached. The firm, which also owns a stake in the San Antonio Spurs, is expected to own in the neighborhood of 12.5% of the Celtics when the deal is finalized—it is lower than its initial commitment. The NBA’s private equity rules cap the stake that a single firm can own at 20% of the team.

The investment group also includes Rob Hale, a current Celtics investor, and Bruce A. Beal Jr., president of Related Companies.

Aditya Mittal graduated from the University of Pennsylvania’s Wharton School and lives in London. In 2021, he succeeded his father as CEO of ArcelorMittal.