How do I gain confidence without being arrogant?

I've never been a confident person. I've always held myself back and not had much faith in myself. I'm the polar opposite to my older brother, which I guess in a way is why I lack confidence so much. He is always brimming with confidence, but to the point where he is arrogant and cocky. I never want to be like that because sometimes it's really knocked me down the way he has acted. I just want to be able to be sure of myself without hurting others.