My son is now 20, but I started him off when he was very young, always believing a man should know how to cook (well, everyone, but...) He'd help out by grating cheese, stirring something, measuring ingredients, etc. His interest really took off when he found a package of Ramen noodles (the cheap, 10 for a $1 kind). I'd bought them when he had a surgery (so 5 or 6), but never ended up using them. He'd never had them, and when he realized they would just be noodles and broth, he wanted to know if he could add anything. By the time he was done, he had a full-blown soup with carrots, celery, onions, ground beef, and probably other random stuff. It was actually pretty good.
Ever since, he has enjoyed trying new things in the kitchen. He's living at home while going to the community college, and I swear that teaching him to cook was one of the best moves I ever made. He is trying different techniques, different "ethnic" foods (we recently got an Asian market in our little town, and it's been awesome-- he even made sushi), etc. He'll look up stuff online and try it out. A couple weeks ago he made pizza with no sauce, figs, bacon, gorgonzola, and a little avocado oil. It was surprisingly delicious. Earlier this week he made some kind of "Nigerian street vendor" beef kabobs (used a lot of peanut and ginger powders for the rub, and was also delicious).
I wanted him to be able to follow a recipe, as well as learn a little "dump cook by feel/taste" cooking. He's far exceeded my expectations and has become quite the cook.
One thing I did with him when little was give him a recipe book and let him pick new things to try. It helped keep things interesting!