Guy's Behavior

Why did he say I can sit next to him?

I was hanging out with a group of friends and there is a guy I kind of like that is a part of my friend group. He has a girlfriend but I have never met her, he brings her up sometimes. I am not sure how serious they are. Out of respect to his relationship and to guard my heart I have never told him I like him or anything like that but this night we were hanging out a few things happened. We were hanging out in the living room but sitting space was limited, my friend that owns the house pulled it out a folding chair and told me I can sit in it. Then he jumped in and told me "You can sit here." pointing next to him in a two seater. There was a girl next to him but not close. This put me in a bind and I didn't know if to sit in the folding chair or close next to him, standing there indecisive he tells me for a second time that I can sit next to him, so I gave in. That put me in between him and the other girl. The other thing that happened that night is that when we were leaving, we all gave goodbye hugs, he gave the other girl a side hug but he gave me a hug with both arms wrapping around me. One on my shoulder and the other kind of on my lower back, while letting go of our embrace he sort of stroked my back and squeezed my back with his hand. I acted natural, trying not to give it a lot of thought. We have seen each other since but haven't really hung out like that again to where we have an opportunity to sit next to each other. So why did he tell me that I could sit next to him when he could have said nothing since there was a folding chair? And what is up with the hug? Any ideas?
Why did he say I can sit next to him?
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