Short answers, pulled from the story.
The Valentinian dynasty was founded by Gratianus Funarius, a senior Roman army officer from Cibalae in Pannonia Secunda, whose sons Valentinian I and Valens were both made Roman emperors in 364. Valentinian I is considered the dynasty's first emperor, acclaimed augustus at Nicaea on the 25th of February 364.
The Valentinian dynasty reigned over the Roman Empire from 364 to 392 and again from 425 to 455, lasting nearly a hundred years in total. An interregnum from 392 to 425, during which the Theodosian dynasty ruled, separated the two periods.
At the Battle of Adrianople on the 9th of August 378, the eastern emperor Valens was killed by an arrow along with an estimated fifteen to thirty thousand Roman soldiers, roughly two thirds of his forces. Ammianus Marcellinus and Paulus Orosius compared the defeat to Rome's catastrophe at the Battle of Cannae in 216 BC.
The Valentinian dynasty oversaw a decisive shift from religious toleration toward Christian supremacy. Valentinian I was personally tolerant, but his successors moved toward enforcing Nicene Christianity. Under Theodosius I, all cult worship of the gods was forbidden on the 8th of November 392, and Bishop Ambrose of Milan forced Theodosius to publicly repent after the massacre of Salonica in 390.
Rome was sacked on the 24th of August 410 when Alaric and the Visigoths entered the city and plundered it for three days. The sack occurred during the Theodosian interregnum, when Honorius, a Theodosian, was the western emperor.
The dynasty originated from Cibalae, a town in the Roman province of Pannonia Secunda in the western Balkans, corresponding to present-day Vinkovci in Croatia. Because of this origin, the Hungarian historian Andreas Alföldi called them the Pannonian emperors.