The heirs of Albert Reimann Jr., who built one of Germany’s largest business empires, maintained for decades that Mr. Reimann and his father had been reluctant Nazis during World War II. Yes, they said, it was regrettable that the company employed slaves and prisoners of war in its chemical factories, but that was the nature of business during the war years.

This weekend the Reimann family decided to change its tune, offering an abject apology for the behavior of Albert Reimann Jr., who died in 1984, and Albert Reimann Sr., who died in 1954.

“They belonged in jail,” a family spokesman told the German newspaper Bild.

The current generation of Reimanns deserves credit for this striking apology. It cannot be easy to publicly condemn a father and a grandfather. Yet the timing of the apology, more than 70 years after the crimes in question — and long after most of the victims would have been able to hear it — raises hard questions about Germany’s failure to hold corporations accountable for wartime crimes, and about the nature of corporate accountability for past misconduct.

The Reimanns, father and son, ran the chemical company now known as Reckitt Benckiser, or RB, probably most familiar to Americans as the maker of Lysol. New research, based in part on materials that have been in the family's possession for decades, shows the two men joined the Nazi Party in 1931, when it was still a fringe movement. They donated to the party and displayed its banner outside their factory. “We are a purely Aryan family business that is over 100 years old,” the younger Mr. Reimann wrote in a letter to Heinrich Himmler, the leader of the SS. “The owners are unconditional followers of the race theory.” During the war years, the business prospered — in part because a third of the work force was employed involuntarily.