No currently reigning family employs the style, although it was used most recently by the younger sisters of the late Grand Duchess Charlotte of Luxembourg.
Since Grand Duchess Charlotte's marriage to Prince Felix of Bourbon-Parma, all of their male-line descendants have used the style Royal Highness, which he bore.
A reigning grand duke, his heir apparent, and their spouses would use the style of Royal Highness.
Other grand ducal families had either ceased to reign as grand dukes by the time this system developed following the 1815 Congress of Vienna or accorded only the style of "Highness" to cadet (Mecklenburg-Schwerin, Mecklenburg-Strelitz, Oldenburg, Saxe-Weimar).
By the time the system of different classes of Highness came into regular use for the relatives of rulers (in the eighteenth century), the Tuscan grand dukes were also members of the House of Austria.