Helen of Greece and Denmark
Princess Helen of Greece and Denmark was married to King Carol II of Romania prior to his accession, and was the mother of King Michael. She is noted for her humanitarian efforts to save the Romanian Jews during the Second World War, which led to her being awarded the honorary title of Righteous Among the Nations
Helen was born in Athens, the third child and first daughter of the future King Constantine I of Greece and Sophia of Prussia. Helen had three brothers, each of whom reigned as kings of Greece George II, Alexander, and Paul and two sisters, Irene and Katherine.
Source: Wikipedia