tbf, a lot of non-Jews were in camps, whether they were Resistance, Jehovah's Witnesses, homosexuals, Slavs, Communists, Roma/Gypsies, or just plain refused to cooperate in some way. One very famous victim of the Holocaust, Maximilian Kolbe, was a Roman Catholic priest who volunteered to take the place of a stranger and was killed at Auschwitz.
The Dutch have some of the best genealogy records on Earth, so with a little research you should be able to determine the truth.