She was the daughter of Maximilian de Beauharnais, 3rd Duke of Leuchtenberg (first cousin of Emperors Napoleon III of the French and Francis Joseph I of Austria) and his wife Grand Duchess Maria Nikolaevna of Russia.
Max and his first fiancee Helen Vladimirovna were thus both of Romanov lineage:
Nicholas I--Maria-Maria--Max
Nicholas I--Alexander II--Vladimir--Helen
Marie and her siblings (Nicholas, Eugen, Eugenia, Sergei, and George) were styled Prince/Princess Romanovsky and Nicholas I extended the rank of Imperial Highness to his son-in-law ,a rank he was entitled to as a descendant of the extended dynasty of Napoleon I . Interestingly, or perhaps not surprisingly, given the reported lifestyles of some of their male (and female) relations, Marie, with the help of Grand Duchess Eleonore of Hesse and Queen Charlotte of Württemberg, set aside a fund meant to produce pamphlets persuading both female and male royal figures that their prominent roles in society meant they should be examples of moral purity. Marie died in 1914 a couple of months before the outbreak of WW1.
Through her father's lineage, Marie's aunts included Queen Josephine of Sweden and Empress Amelie of Brazil.
Marie's siblings Eugenie & George married into the houses of Oldenburg and provided more Romanov links. Her brother George was the first husband of Grand Duchess Anastasia 'Stana' before they divorced and she remarried GD Nicholas N. Eugenie's son was Peter of Oldenburg, GDss Olga's first husband. The 2 were more 'Russian' than Marie who didn't visit Russia as much after her own marriage.
