Three of the world’s biggest private equity firms are among a number lining up initial public offerings of their larger European assets over the next six months, according to three bankers close to the deals.

The news is especially significant given the scale of the private equity portfolios controlled by the three companies, Blackstone Group, KKR and Advent International, each of which has dozens of holdings. In late 2009, the last time buyout firms began preparing a push for IPO exits, Blackstone's chief executive Stephen Schwarzman told investors the firm was considering listing as many as eight of its portfolio companies.