Prince Heinrich of Hesse Darmstadt (1838-1900) is interesting as regards the arms of Morganatic houses in the fact that he actually fathered two of them.
By his first morganatic marriage in 1878, to Caroline Willich von Pöllnitz, later created Baroness of Nidda (1848-1879), he had one son, Karl (1879-1920), created Count of Nidda in 1883
The arms of the Counts of Nidda were Or, on a chief Sable two Mullets of Eight points in fess Argent:
-which was simply a re-use of the territorial arms of Nidda born in the greater coat of arms of Hesse-Darmstadt, and had originally been born by the family that ruled Nidda in the 1200s but had become extinct.
Prince Heinrich married for a second time, again morganatically, in 1892 to Emilie Hržić de Topuska (1868–1961), created in 1895 Baroness of Dornberg
By her he had a second son, Elimar, Baron of Dornberg.
The ancient arms of the medieval Lords of Dornberg had been Azure, three Lozenges Argent:
-for the arms of Elimar, the Azure in the arms of the medieval Lords was merely replaced with Gules.