Jack and JLL went up the hill, to fetch a pail of ... portfolio companies? JLL Partners (formerly Joseph, Littlejohn & Levy) is anything but child's play. The private equity firm seeks controlling stakes in middle-market companies in a range of industries, including broadcasting, chemicals, consumer products, financial services, health care, transportation, and manufacturing. An active investor, it works with its portfolio companies' management to help develop strategy, foment growth, and make acquisitions. JLL Partners diversified beyond private equity in 2010 when it formed alternative asset manager JLL Capital Partners, which invests in distressed debt of middle-market firms.