The Japanese insurer, through its subsidiary Mitsui Sumitomo Insurance, bought the stake for $1.44 billion from Massachusetts Mutual Life Insurance Company.
The private debt specialist, which operates a dedicated secondaries strategy, has reportedly held talks with several international investors.
The passive minority investment will reportedly strengthen the Swiss private equity firm's balance sheet and support team expansion and alignment with LPs.
The investment in the Brazilian alternative asset manager will be made through a primary capital injection, with no existing partners selling their holdings.
A non-binding term sheet also gives O3 the option to increase its ownership in the Hungarian fund manager if AUM grows significantly.
Sterling is a mid-market private equity firm focused on the business services and distribution sectors.
The GP staker will support the Australian property investor's growth across distribution, product development, and institutionalization.
In addition to seed capital, the GP stakes firm will also provide support across talent acquisition, capital formation, and operations.
The deal marks the sixth investment made by Armen's inaugural GP stakes fund, which targets a portfolio of European alternative asset managers across different strategies.
The management buyback closes out AMG's investment in the former Comvest business, with total proceeds of about $294 million.
