@monkey123 that is complete nonsense, and not at all how Japanese works.
It is absolutely completely common in Japan for young children of either sex to refer to each other as such, and childhood friends typically often doing that into adulthood simply because it's weird to suddenly change something that has been convention; parents will also continue to refer to their children as such well into adulthood typically.
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kun is also frequently used for females, in particular by employers, teachers, and others who are formally ranking above them.