When is "too young" to get married?

I'm of the opinion that committing your life to the one you love isn't something that should be delayed for my convenience. Although I'm only turning 21 in May, I know that my boyfriend and I will be married and that he's the one, but my family and friends suggest I wait till I'm 25. If you've been married young, would you consider it challenging? If you're divorced , did age play a role in that? We've been together a year and a half by the way, and would like to be engaged by next year.