He quarrelled with Lemot in 1821 and never finished the project, which was left to his successor, Pierre-Louis Van Cleemputte. His niece, Justine Crucy, married Louis-Prudent Douillard, an architect, in 1821 and in 1823, another niece, Zita Crucy, married Louis-Prudent's brother Constant, an architect too, who designed some of the hospitals of Loire-inférieure, notably "St. Jacques General Hospital" in Nantes, and the "place du Sanitat" in the same town. Justine and Zita were daughters to Louis Crucy (born 1756), Mathurin's brother. On the 4 October 1785, in the Saint Similien church in Nantes, Louis and Mathurin Crucy had themselves married sisters Le Roux, Françoise and Marie Françoise.