Can I switch sim cards in order to set up iphone 4s?

I bought a iphone 4s from my cousin without a sim card, it worked fine but I restarted everything so that I can add my information and all that. But of course it doesn't let me set up my iphone until the iphone is activated. My brother also has the same kind of iphone and he has a sim card but his sim card isn't activated so he just uses it as an ipod. I also want to use my iphone as a ipod but like I said I can't activate it unless I have a sim card.

So can i just use my brother's sim card to activate it and then take it out and use it?

Added (1). Welp, apprently my brother doesn't have a sim card either but it doesn't say (no sim) in his iphone… Oh well, i don't know how to delete this quesiton either…

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