Why a guy questioned me about another guy?

So this guy I talk to often was talking to me and I told him this guy text me to just chit chat.

The guy I was talking to then asks me what I would do if that guy would text me that he missed me.

Is he jealous the other guy text me to chat or does the guy I talk to often has feelings and was testing the waters.

I'm a bit confused because ever since then he been acting differently kind of towards me now.

Why a guy questioned me about another guy?
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