Investment banker Adebayo Ogunlesi is set to sell his firm Global Infrastructure Partners (GIP) in a $12.5 billion deal to BlackRock, the biggest asset management company in the world.

As part of the deal, Blackrock is to pay $3 billion in cash and offer Mr Ogunlesi and five other co-founders of GIP 12 million shares in Blackrock.

This will make the six individuals the second biggest shareholders in the global asset management giant.

In a statement released on Friday, BlackRock said it would also appoint Ogunlesi, who is GIP founding partner, chairman and CEO, to the board at the next scheduled board meeting after the close of the deal.

“The combination of GIP with BlackRock’s highly complementary infrastructure offerings creates a comprehensive global infrastructure franchise with differentiated origination and asset management capabilities,” the statement said.

BlackRock said GIP’s acquisition aligns with the vision of Laurence Fink, its chairman and CEO, to transform the firm into a key player in the growing market for private and alternative assets.

It added, “The over $150 billion combined business will seek to deliver clients market-leading, holistic infrastructure expertise across equity, debt and solutions at substantial scale.

“Marrying the proprietary origination and business improvement capabilities of GIP and BlackRock’s global corporate and sovereign relationships provides a platform for diversified, large-scale sourcing to support deal flow and co-investment opportunities for clients. We believe bringing GIP and BlackRock together will deliver to clients the benefits of broader origination and business improvement capabilities.”

Commenting on the acquisition, Fink said the deal is “one of the most exciting long-term investment opportunities.”

GIP has $106 billion invested in infrastructure, while Blackrock manages $10 trillion worth of alternative assets.

Ogunlesi, an alumnus of King’s College Lagos and Harvard University, was chief client officer and vice chairman at Credit Suisse First Boston before leaving to start GIP.

His profile grew in Nigeria after GIP bought Gatwick Airport. The main assets of GIP include Sydney, the Port of Melbourne, the Suez Water group, extensive green energy holdings, and a stake in a big shale oil pipeline.