What does it mean when a guy calls a girl "bro" who once told her to not call so?

I've met this guy 5 months back via a friend. We've been in touch since then. Initially during first days of our friendship, during a conversation I once called him "bro" (because I'm used to calling "bro", "man" as a have a brother of more or less the same age ). He immediately told me not to call him so. I understood and never till date called him "bro" . During this time span, I started liking him. Once, during a text conversation when I asked him something he told " sure bro :P " . I thought he told casually and didn't ask him about it. It repeated many times after that, but every time he texts bro he never forgets to add this emoji " :P " What does he mean? Why is he doing like that? What is he trying to convey? Does he add that emoji so that I don't get offended? What are his intensions?
What does it mean when a guy calls a girl "bro" who once told her to not call so?
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