Ismail I's father did not speak any other language than Turkish until he learnt Arabic and Persian later on.
He never learnt or spoke Kurdish.
There are some theories that his 12th grandfather was Firuz Shah a man with Kurdish origin.
But the thing is it is disputed if his 7th grandfather is his 6th grandfather's father.
I mean his 7th grandfather being his 6th grandfather's father is just a theory.
We also know that his 6th grandfather's teacher sheihk Zahid Gilani once called him pir-i Turk.
So thats why some Turks claim his ancestry was Turkic.
One thing was for sure that up until his father they were so Turkified that their mother tongue was Turkish while they couldnt speak Kurdish.