Is it weird if his friends already know about me

Guys don't mention someone to their friend group unless they think there's something there. It's different from mentioning a date in passing. Bringing you up means he's thinking about you between hangouts, he's picturing you in his life, and he's comfortable enough with the idea that he talks about it out loud. This is pre-investment behavior. It suggests he sees potential and isn't keeping you compartmentalized.

The timing concern makes sense, but four dates plus friend mentions is not fast. It's normal. You're past the first impression phase. He's already evaluating whether to keep going, and the fact that he's doing it openly rather than secretly is what matters.

Your response should accomplish three things. First, normalize it. Don't act surprised or concerned because his friends knowing is a neutral fact, not a crisis. Second, show you're unbothered and can take it lightly. Third, keep the ball rolling forward without suddenly getting serious or distant.

You're not saying 'cool, we're basically married' and you're not saying 'pump the brakes, buddy.' You're somewhere in the middle. You heard, it's fine, I'm interested too, and nothing changes about how this actually works. The tone is light but clear.

Don't wait days to reply to this. It's a casual thing he said, and dragging it out makes it feel like a bigger deal than it is. A same-day or next-morning response keeps the conversation natural and shows you're not overthinking.

Once you reply, don't chase with follow-ups about it. If he wants to talk about you meeting them or making things official, he'll bring it up. Your job right now is just to respond in a way that says you're cool with his interest without forcing the next step. Let his actions over the next few dates tell you whether he's serious.