His friends invited me to guys night?

I’ve been seeing this guy (non exclusively) for 8/9 months now. I know he talks to his friends about me and I’m also pretty close to them already. It’s gone to a point in where if my guy can’t make it they want me to go either way, even if it’s all guys hanging out.
They treat me as his girlfriend (ask me about him, ask me permission before doing pranks on him, thank me for making him happy, respect me a lot, take care of me if he’s not there, etc). How good is this? Is this a sign that things are getting serious? His best friend even mentioned to me how my guy talked to him about me and then they all invited me to a guys night they are having tomorrow.
His friends invited me to guys night?
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