According to two persons familiar with the situation, Blackstone Group has purchased a minority investment in Nautic Partners, a middle-market private equity firm that focuses on healthcare, industrials, and services companies.

Blackstone, one of the world's largest private equity companies, purchased the holding through its second GP stakes fund, which specializes in purchasing minority stakes in other funds in order to profit from both the target's fees and investment gains.

The deal's terms were not revealed.

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Nautic has completed a $3 billion fundraising round for its eighth private equity fund. Its typical investment amount ranges from $50 million to $250 million. According to one of the individuals, the firm, which had been approached by a number of possible suitors before reaching an agreement with Blackstone, aims to use Blackstone's cash to engage in acquisitions.

Blackstone just completed the financing of a new fund, the Strategic Funds Holdings II fund, which closed with $5.6 billion in investor capital last month.

Blackstone is one of a select group of firms that has made a successful business out of buying minority holdings in other private equity firms.

While the trend began a few years ago as a number of senior partners sought to quit the company they founded, it has gained traction as new executives seek to expand into other businesses or require funds to hire new personnel.

The three major players in the so-called GP stakes market, Blue Owl, which manages Dyal, Blackstone, and Goldman Sachs' Petershill Partners, have all recently raised billions of dollars for new funds.

Blackstone is one of a select group of firms that has made a successful business out of buying minority holdings in other private equity firms.