Typical friend behavior or nahh?

So like I’m friends with this guy for bout 5 months and we’re practically best friends now. I’ve never been this close to anyone before. And he’s a really touchy person, like he has a habit of touching my arms, patting my head and being very affectionate in general. Mostly towards me but he does this to others too. Recently, he started to become clingy and lean on me and hold my hands (interlocking fingers and all that ;-;) when we hang out. I don’t mind it because we’re comfortable with it BUT the thing is he has a girlfriend Σ(っ°Д °;)っ and idk if this behavior is considered normal by other ppl ╥﹏╥ what do y’all think? (๑•ㅂ•)و✧