Simpson Thacher & Bartlett is advising longtime private equity client KKR on its purchase of a 24.9 percent stake in Nephila Capital, an $8 billion firm that provides reinsurance for catastrophes like earthquakes, hurricanes, and other natural disasters.

While the financial terms of KKR’s investment in Nephila have not been disclosed, a press release announcing the transaction states that KKR will acquire its shares from Nephila’s management and minority stakeholder the Man Group, the world’s largest publicly traded hedge fund manager. (Man Group’s stake in Bermuda-based Nephila will be reduced from 25 percent to 18.75 percent following the transaction.)