He always says im his sister?

Even when we talk he says: you know sister it’s bla bla bla… like he says it alllloot it s not normal.
All his friends want to be with me. He said to me once that i m smart beautiful and well educated girl. And he loves the fact that i do not wear make up at all! All his friends flirted with me but i m a serious girl and funny at the same time.
He acts weirds when we are with his friends he says bad words front of me like he shows to his friends that he is not interested in me. But when we are alone he is so sensitive and sweet.
Does he like me or what? Even if he calls me sis?
He always says im his sister?
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