House of La Tour d'Auvergne
In the eighteenth century, as dukes and lesser noblemen arrogated to themselves the title "prince de X", more of the foreign princes began to do the same. Like the "princes du sang" (e.g. Condé, La Roche-sur-Yon), it became one of their "de facto" prerogatives to unilaterally attach a princely "titre de courtoisie" to a "seigneurie" which not only lacked any independence as a principality but might not even belong to the titleholder, having merely been owned at some point by his family (e.g., "prince d'Harcourt" and "prince de Lambesc" in the House of Lorraine-Guise; "prince d'Auvergne" and "prince de Turenne" in the House of La Tour d'Auvergne; "prince de Montauban" and "prince de Rochefort" in the House of Rohan; "prince de Talmond" in the House of La Trémoïlle). Nonetheless, these titles were then passed down within families as if they were hereditary peerages.