The newly combined entity is expected to double the size of Coller's secondaries business in less than four years.
Under the non-binding agreement, O3 may increase its ownership in the social impact investor if certain fund launch and fundraising milestones are met.
The secondary market specialist will remain independently managed by its existing leadership team, with no changes to its investment strategy.
The firms have reportedly held discussions over a potential tie-up, which would boost Ares' secondaries AUM closer to the $50 billion mark.
The GP stakes deal builds on a 2024 strategic partnership, which established Lazard Elaia Capital as a technology-focused private equity investment platform.
The commitment comes just eight months after Wafra first invested in the French manager.
Founded by Rob McGrath, Overbay is a Toronto-based private equity secondaries specialist with around $3 billion in AUM.
The multi-strategy hedge fund manager provides institutional investors with exposure to cryptocurrencies and other digital assets.
The addition of Glouston Capital Partners will support the Natixis affiliate's efforts to expand its secondaries strategy and US distribution reach.
The deal will expand Mercer's private markets platform, adding expertise in secondaries and evergreen vehicles to its offerings.
