The Chofetz Chaim was still alive 85 years ago. I didn’t know any of his children were so not frum that this great/great/grandchild would have almost no Jewish knowledge.
I heard a story that 2 grandchildren of the chofetz Chaim met sometime after the war one was male and the other female. it seems the female went off the derech and the male asked the female to relate a story of their grandfather. The woman said, I asked Zaide why he insists on living such a backward lifestyle and doesnt become modern and I forget what he said, but it was something about what modern life brings that is negative
The reason I mention this is because it is very possible the Chofetz Chaim has non-relgious decendents. I also heard he had a non-religous son