(Reuters) - Blackstone Group LP (BX.N), the world’s largest manager of alternative assets, said on Thursday a key measure of its earnings rose by 5 percent, helped by large gains in its private equity unit and strong performance by its real estate, credit, and hedge fund businesses. Blackstone followed its peer Apollo Global Management (APO.N) in reporting strong appreciation in its buyout funds and higher profits as both benefited from the stock market rally and a string of asset sales.