Rebbe's family were 'stateless jews' so they got kicked from Germany & France as such. Ended in Warsaw Ghetto on the way to gas chambers. In order to get out, nazis had ladies of child-bearing age sterilized. That's why Rebbe never had children. Worse, neither Rebbe nor his father-in-law provided any leadership or tried to save Jews at that time. They only cared about their own skins. Before Rebbe died, he cried "it had to happen" refering to Shoa, as recorded in Sihos. Not a happy story.
Israeli troops shoot, injure Palestinian crossing Gaza border fence (Haaretz)
from the article: The half-Jewish Nazi who saved the Lubavitcher Rebbe