Why does my friend act so weird?

A friend of mine is a super flirty drunk. Even when he's not drunk he'll flirt with me. When we're alone he tells me he wants to take me out sometime for a good time. He does things like hold my hand, stare at me constantly, always stands/sits by me, tells me he'll always be there, and teases me. I went on a date with someone he knew and that person said they were shocked I showed up because they were under impression I was involved with my guy friend. This person never met me before. I've also heard my friend tells people I'm a sister to him and always tells our siblings when we hang out alone. I confronted him about staring and he just smiled and said "nothing" and looked away. I didn't even know if I wanted to still be friends and he said he does and that he's made comments about me before but not to overthink it and that he'd tell me if he didn't want friendship. He said we're friends we just can't be close friends? I told him I think of him as a brother and he didn't respond. I don't get it, what's his deal?
Why does my friend act so weird?
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