I just checked it out and apparently it's a merger, where both are equal partners:
"2005: Coors merges with Molson, a combination of two equals and the creation of a new company with the operating scale and balance sheet strength to take a leading role in the consolidating global brewing industry. Combined beer sales make Molson Coors Brewing Company the world's fifth largest brewer."
It does say that Coors merged with Molson, which does kinda sound like Molson has a controlling interest. I like Molson beer better anyway.