I voted 'sort of.'
My mom has a had a relaxer for YEARS. But I was around when it was press and curl, so I would say she's a true 3C with a tiny bit of 3B thrown in. Her hair is thin and fine. Her father on the other hand was a 2B/3A (I say was because he barely has any left.) Her mother was probably a 4A judging by my mother's sisters and brothers. And her father's mother was a 2B.
I am a 3C probably a 3D (I a 100% a curly head, but my curls are very small.) My hair is full and fine. (not thick) My baby sister (before the dreaded relaxer) is also a curly, her curls are even smaller than mine. Her hair used to be very very thick. Now it's just... blah.
And my father. I have no idea but he's probably a 4A. But who cares.