By the death of his father on the 1st of November 1894 he became emperor, and on the 26th of that month he married Princess Alix of Hesse (a grand-daughter of Queen Victoria), to whom he had been betrothed in the presence of his father during the latter's last illness.
The first line of its counts, supposed to be descended from the dukes of Normandy, had as heiress Alix (died 1227), who married Raoul (Ralph) de Lusignan, known as the Sire d'Issoudun from his lordship of that name.
Du Cange discovered and quoted a deed of donation by him dated 1207, by which certain properties were devised to the churches of Notre Dame de Foissy and Notre Dame de Troyes, with the reservation of life interests to his daughters Alix and Damerones, and his sisters Emmeline and Haye, all of whom appear to have embraced a monastic life.
On the next day the emperor William officially announced the betrothal of the Cesarevitch (afterwards the tsar Nicholas II.) to the princess Alix of Hesse, a granddaughter whom the queen had always regarded with special affection.
Enguerrand IV., sire de Coucy, died in 1320 without issue and was succeeded by his nephew Enguerrand, son of Arnold, count of Guines, and Alix de Coucy, from whom is descended the second line of the house of Coucy.