In Standard German, "Ich hab(e) dich lieb" is just a slightly toned-down version of "Ich liebe dich." Normally you wouldn't say it to a friend, unless you are trying to turn that friendship into a romance. You may say it to your parents, your aunt, your cousin etc., and you may say it to your spouse or lover once in a while, provided you say "I love you" often enough too.

Some people may say "Ich liebe dich" also to their close relatives, but I think most prefer "Ich hab(e) dich lieb."