Adolph Coors Co. and Canada's Molson Inc. on Thursday agreed to merge in a deal that would create the world's fifth-largest brewer by volume. The fate of the deal remained unclear, however, due to a last-minute takeover offer for Molson from Ian Molson, a one-time deputy chairman who resigned in June after a falling out with Chairman Eric Molson, his cousin. Under the Coors-Molson agreement, Molson shareholders would control about 55 percent of the combined company, which would remain largely in the hands of the founding Molson and Coors families. The deal would solve expansion issues for both companies, which...