What are the limits of the prefix 'step' to describe relationships?

Is my mother's step-father, my step-grandfather? To what extent is it usual to extend the prefix 'step'?

Can we speak of 'step-cousins', step-aunts and step-uncles etc? If we can it must make for considerable complication in how such relationships are defined.

Of the combining form step-, Oxford Dictionaries only says:

denoting a relationship resulting from a remarriage

Past immediate step-parents or step-siblings, I no longer find the distinction useful.

Introduce your mom's stepfather as "My mom's stepfather."

Likewise with your stepmom's sister, your aunt's stepdaughter, and so forth.

I did a quick NGrams, and -father has 106, to -grandfathers 9, -uncle -4 and cousin 1. And father was far more common in the 1860s than that.

I left out the female side, aside from half of cousin.

So it appears the more distant the relation, the frequency of stepping drops by about a factor of 10.