Connecting new 2014 Mac Mini and 2009 Mac Book Pro thru one VGA display
Both MacBook Pro and the Mac Mini have Mini-DisplayPort on them. 
You can connect the Mini-DisplayPort to an Minii-DisplayPort-to-VGA converter and then, 
connect VGA cable on it to a two-port VGA DDM KVM switch, such as ConnectPRO's UR-12+.

I had been using this configuration for years without problem.