咱哥儿谁跟谁啊 is an expression in northern dialect of Chinese, which means "we (the two people in the conversation) are true friends". It further indicates the meaning of "You are welcome/ Don't mention it". It also indicates the friendliness and directness of northern Chinese people.
More frequently we may say 咱哥儿俩谁跟谁啊, 咱哥儿俩 means "we", 谁跟谁 literally means "what is the relationship between us", but in this sentence to emphasize and indicate "Our friendship is so close (there is no need to doubt or question the relationship)" . It is like a 反问句 rhetorical question in Chinese, but the question mark is omitted.
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