Both Sikorski and Piasecki created early twin engine helicopters. I believe Sikorski was actually first with the CH-37 Mojave sold to the US Marines in 1954.
there are a few twin rotor helicopters. The Chinook is possibly most famous.
Canadian Helicopters was created in 1987.
Universal Helicopters was created in 1963.
Carson Helicopters was created in 1963.
Bajan Helicopters was created in 1989.
Bristow Helicopters was created in 1953.
Hughes Helicopters was created in 1947.
Columbia Helicopters was created in 1957.
Russian Helicopters was created in 2007.
Helicopters - band - was created in 1980.
Bendix Helicopters was created in 1942.
Gulf Helicopters was created in 1970.