HI Daniel,
I walked it two years ago at the age of 19, and while I was the youngest person there more or less, there are lots of people in their 20s and early 30s. I'm walking again this year at the age of 21 as well and I expect to find the same. However, like those before me said, it depends on the season. I walked (and am walking) in spring, where there's probably a lower ratio of younger to older than there is in the summer.
But really, most of the really good friends I made last time were 10-15 years older than me. The thing is, the Camino makes for a level playing field. People don't think of you as being far younger than them, and you tend to, likewise, forget that you are. You're all out doing the same thing, regardless of the stage of your life that you're at, and it makes for some real connections. Not to mention the fact that I also made some great friends in people two, three, four times my age! The Camino presents a unique opportunity to pick the brains of people you might not normally speak to with any depth.
Embrace it. Enjoy it. And buen camino.