He was the nephew of the Polish general Prince Józef Antoni Poniatowski.

[1][2] Jozef Michal Poniatowski (Joseph Michael Xavier Francis John) was born Giuseppe Michele Saverio Francesco Giovanni Luci in Rome, the son of Stanisław Poniatowski and Cassandra Luci.

Poniatowski was sent to Paris as plenipotentiary by Grand Duke Leopold II.

He was created the 1st Conte di Monte Rotondo on 20 November 1847, and the first Principe di Monte Rotondo on 19 November 1850[3][better source needed] by Grand Duke of Tuscany Leopold II.

Together, they had one son who was born in Florence : Poniatowski died and was buried in Chislehurst, Kent in 1873.