After a decade working together, Rem Koolhaus and Joshua Prince-Ramus are splitting up, with Prince-Ramus taking all of the architecture firm’s 35 members of the New York office with him. “So, no hard feelings, no intrigue? No, both men insist, their parting is simply a response to unfolding circumstances and an attempt to clarify issues of authorship and control. ‘It ultimately became a clear decision, but not an easy one,’ said Mr. Prince-Ramus, 36. ‘The sadness is something we deal with in private,’ said Mr. Koolhaas, 61.”