My paternal grandmother taught me. She used to knit, crochet and quilt like a bad ass, though that was before the arthritis took over her hands. I have two quilts from her, dozens of hats, and at least two sweaters. In fact, I think I was the only grandchild to get this intarsia sweater that had a big bear on the back. She made it too big but I wore it anyway. I know I have it in a box downstairs somewhere.
I went to visit one summer and she was crocheting a large afghan. For some reason I asked what she was doing and showed me the basic stitches. I took to it immediately. (Now I want to go find my old swatches!) I came home, bought some yarn and made a scarf. I went back to visit a month later and she decided to teach me how to knit. It was a lot harder, but after a lot of practice I learned it as well.
Now I'd say I'm equally talented in both crafts, though I find it easier to design in crochet. I'm really glad I can do both; I know a lot of people that can just do one, and that the other is so difficult, but for me I can so straight from crochet to knit and back again and it doesn't phase me at all. There are definite differences, and each has their strengths and weaknesses, but I like how I can do both.