Short answers, pulled from the story.
Flavius Valentinianus founded the Valentinian dynasty and was born in Cibalae, now Vinkovci in Croatia. He rose through the ranks of the protectores to become tribunus in 357 before being elected emperor by the army.
Valens became co-augustus on the 28th of March 364 after his brother arrived in Nicaea on the 25th of February 364. This division split the empire along linguistic lines with Latin in the west and Greek in the east.
The Battle of Adrianople killed Emperor Valens along with two-thirds of his forces estimated at fifteen to thirty thousand soldiers dying that day. Corrupt official Lupicinus had seized chieftains Fritigern and Alavivus triggering a full-scale attack near Marcianopolis.
Ambrose became bishop of Milan in 374 and threatened Theodosius with excommunication following the massacre of Salonica in 390 until public repentance occurred. He established the precedent that man must serve God first before any emperor.
Valentinian III was the last emperor of the Valentinian dynasty and died in 455 marking the end of the western empire. A thirty-year gap existed where the Theodosian house ruled while the Valentinian line lay dormant before restoration.