It was established on 3 July 1738 by Charles of Bourbon, King of Naples and Sicily, to celebrate his marriage to Princess Maria Amalia Walburga of Poland and Saxony.
As main duty, the Knights had to "increase, at all costs, the Holy Religion" and "virtuously operate” to be "an heroic example of piety towards God and loyalty towards their Prince".

The Order is formed by only one Rank of Knights with golden collar, fess, cross and plate.

The decoration is formed by a cross with four forked arms edged in gold, bordered by a fess of white enamel, with flames in red enamel edged by four golden lilies.
On the recto, the image of St. Gennaro with the cruets and the Pastoral, in golden, white red blue and green enamels; on the verso, in the middle, the Cruets in golden and red enamels, placed on a golden Book of Gospel, all bordered by two palms in green enamel.

The ribbon is red and swayed.

The inscription is "IN SANGUINE FOEDUS".

The present Grand Master is HRH Prince Charles of Bourbon Two Sicilies, Duke of Castro.

Other Orders:

- Illustrious Royal Order of Saint Ferdinand and Merit
- Sacred Military Constantinian Order of St. George
- Royal Order of St. George and Reunion
- Royal Order of Francis I