Princess Alexandrine had Down syndrome. The norm was for royalty (even overthrown royalty, like the Prussian royal family) and prominent families to make a secret of children with major disabilities - notably, JFK had a sister who was lobotomized by their politically-oriented father for being a potential embarassment.
Princess Alexandrine, however, was largely treated like her non-disabled brothers and sisters - appearing at events, in family pictures, and in general being acknowledged by her family instead of treated like a dirty secret. She openly attended a school for special needs children, was cared for by a nurse, and would live to the age of 65.
She survived the entire Nazi era?
Yep. She was a royal. While the Nazis were distinctly not monarchists, many of the conservatives aligned with the Nazis were. The chance of them alienating their own support base to execute just one more disabled person was not high.
