Throughout his life, he struggled to preserve the legacy his father had left him, facing the vindictiveness of Richelieu and the jealousy of his half-brother, King Louis XIII. César devoted his life to defending his rank and the benefits his father had bestowed on the House of Vendôme, embodying the soul of a devoted protector.
On the death of Marie de Luxembourg, her only daughter, Françoise de Lorraine, Duchesse de Vendôme and wife of César-Monsieur, inherited a Paris mansion still under construction. César, Duc de Vendôme, thus became the true owner by marriage. It was probably at this date (1623) that the Hôtel des Mercœur was renamed the Hôtel de Vendôme
"Hôtel de Vendôme".
On September 22, 1665, César de Vendôme died in his Hôtel de Vendôme in Paris, a sumptuous residence with some sixty rooms, reflecting the architectural marvels of the time.
The mansion, once located on the rue Saint-Honoré in Paris, was demolished in 1685 to make way for the Place Vendôme, a place that even today evokes dreams and supreme elegance, notably with luxury brands such as Louis Vuitton.