He didn’t want me calling him “bro” lmao?

Ok so I had a sneaky link and playfully I called him “bro“ when we were joking around with eachother and he said “I’m not ya bro”. Guys, what does that mean? Why did he get annoyed like that? And why don’t y’all want certain females to call you bro?
He didn’t want me calling him “bro” lmao?
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