At what age is good to start snowboarding?

My brother is 5 years old, and will be 6 in November. If he wanted to start snowboarding, would it be too soon for him? I'm not talking about jumps and terrain parks, I'm just talking about just getting on the board and going down the bunny slope. He'd have me as a teacher and I'd dedicate my time and effort to help him. But, my question still is, is he still a little too young?