In 1721, the ambassador of France to Russia suggested a marriage between Louis and one of the two unmarried daughters of Peter I of Russia: the Grand Duchess Anna Petrovna (known for her fluency in French) or her younger sister, Grand Duchess Yelizaveta Petrovna. But the idea of a marriage with a Russian Grand Duchess had to be abandoned as there soon arose difficulties relative to religion and order of precedence. Louis was "only" a great-grandson of the king of France and as such was only entitled to the style of Serene Highness. A Russian grand duchess, however, as a daughter of the tsar, was entitled to the style as Imperial Highness.