Henry the Admirable founded the Principality of Grubenhagen in 1291, after the Guelph princes had divided their inheritance.
Ernest originally intended to follow a spiritual career, but after his father's death, he and his brothers Henry II and William jointly ruled the principality.
Because Henry the Admirable had many children (eight sons and eight daughters), it was difficult to supply all the descendants in style.
In 1324, Henry concluded an extensive pact with his brothers Ernest and William under which the territory should be governed jointly, but shortly afterwards the principality was divided.
After his death, on 9 March 1361, he was succeeded by his son Albert I. Ernst married in 1322 Adelheid (or Agnes) of Everstein-Polle (died after 1373), daughter of Count Henry II of Eberstein.