The Kurdish language has different varieties that linguists do not consider separate from Kurdish, with the exception of Gurani and Zazaki, which are considered independent from Kurdish in the opinion of some linguists. Separating Gourani and Zazaki does not have much history and was not discussed until the arrival of orientalists in Kurdistan. But now it is very popular in academic circles. Contrary to its reputation, this issue has not yet been proven, and its theoretical foundations do not have strong arguments. In this essay, by examining the research that has been done in this field, it was found that the basis of all researches is based on two hypotheses. The first hypothesis is the history according to which Gorans and Zazas migrated from the shores of the Caspian Sea to the western regions of Iran; the second hypothesis is linguistic, according to which Goran and Zazaki languages belong to the group of Iranian languages of the Caspian coast. By examining the historical hypothesis, it was found that in addition to the fact that this hypothesis has not yet been proven, there are also evidences and suggestions that prove the opposite. Regarding the hypothesis of linguistics, the paper finds that the arguments presented in this field are not free of problems and some of them are wrong, also the provided arguments in this field are not just linguistic arguments, but rather based on extra-linguistic evidence.