My grandpa worked for GM for 30+ years. He only bought Chevys or Buicks his whole life. My parents only buy GM, my brothers only buy GM, I've only owned GM. Every car my family has owned, new and used, has been a great/reliable car. All GM. "Stick with what works" has worked out pretty well so far.
That being said, I like a ton of different cars and I'm too much of a car enthusiast to limit myself to one manufacturer. I think at some point I'll be the first one in my family to own a non-GM car, and I have no idea what their reaction will be