Carlyle Group LP is gathering as much as $5 billion for a fund that can hold stakes in companies for as long as 20 years, joining private equity firms such as Blackstone Group LP and CVC Capital Partners Ltd. in seeking more permanent capital from investors.

The firm expects to make investments that don’t fit within the mandate of Carlyle’s sixth main buyout fund, which raised $13 billion last year, said three people with knowledge of the matter who asked not to be named because the information is private. Investments could include taking minority stakes in companies and backing family-owned businesses, the people said. The fund would charge lower fees than its traditional buyout offering, they said.