Is being nice flirting?

Is being nice flirting? I've gone out a couple of times with my partner. And I'll be talking to his mates or random dudes and he will come over to me and say I'm flirting or that I want to kiss them just because we will be laughing or having a good conversation. Recently his best mate did put his hand on my lap I was bat shit drunk and didn't realize. Went out for a smoke and he told me that he thinks I'm going to hook up with his mate I apologize and didn't mean to give anybody any signals and we left straight away. Am I in the wrong when his mate put his hand on me? I wasn't saying anything I believe to be leading him on? I do remember being nice to him but nothing I can think of to make him think that was appropriate.

Is being nice flirting?
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