These two theories are unrelated and should be studied separately.

unrelated 是由前缀 un-（表示"不、非"）和动词 relate（相关、关联）的过去分词 related 组合而成的形容词。un- 否定前缀 + related（相关的）构成 unrelated，意思是"不相关的、无关联的"。