Kurdish is an Indo-European
language. It is in the Iranian group. The Ethnologue database or the
article in the online Britannica will fill you in on the basic
details.
The first wave of Indo-Iranian
expansion was lead by the Indics, who managed to sprawl over the whole of
Central Asia, and get to India-Pakistan. How deeply they penetrated what is now
Iran is open to question, but the linguistic evidence says they reached the
South Caucasian area and places thereabouts. The Iranian branch of the
Indo-Iranian superstock would later completely supplant the Indic languages
everywhere except India-Pakistan and parts of Afghanistan.
Mark.