I'm going to spend in the area of the Bieszczady mountains a bit more time this summer.
If I happen to be there again I'll try to find these two graves and take some photos of course.

Eastern name Iwan (Ivan) is an equivalent to Polish Jan.

Nowadays people turn back to old tradition I guess much more than they did or could in the past and celebrate Ukrainian traditions and language.

In this cemetery and many more in this region there are graves with both Polish and Ukrainian inscriptions.
I cannot take pride in the knowledge of history or ethnography, so forgive my cursory explanation

But there appear those who know really a lot and can provide you with the appropriate information and links to some interesting websites...as they have done before

I put a photo showing the location of Ivan's grave, here you have a photo of the church taken when standing above it on the road Zagórz-Komańcza: