This entire region was an integral part of the Roman Empire at the beginning of the study period. It was a source of slaves, soldiers, merchants, and administrators who could be found throughout the empire and the recipient of similar people from elsewhere in the empire. So, if your ancestors lived here in 1000 CE, their ancestors could easily have been from anywhere in the Roman Empire in 1 CE.
Fourth Century Germanic migrations: During the collapse of the Roman Empire, a confusing number of nations used this region as a wrestling mat or passed through en masse. Three Germanic nations figure prominently: the Goths (Visigoths and Ostrogoths), Vandals, and Burgundians. These originated in what is now Southern Sweden and adjacent Baltic islands and, beginning in the first century, began a long migration that took them through Poland and the Ukraine. During the third century, when the Central Asian Huns arrived in the Ukraine, the Burgundians, Vandals, and the western Goths (Visigoths) fled to the Balkans. If your ancestors lived in the Balkans in 500 CE, then their ancestors might also have lived anywhere along the track of these Germanic migration, all the way back to Sweden, in 1 CE.
Fifth Century Slavic migrations: During the fifth century, the Slavs appear in history, having migrated into Eastern and Central Europe and the Balkans from their homeland in the Ukraine and Southern Russia. At this time, Slavic languages came to be spoken from the Baltic shores of Poland to the southern Balkans. Only Romania and Greece, which held onto their ancient languages, and Hungary, which adopted the language of later invaders, have non-Slavic tongues. Nevertheless, the number of Slavic words in modern Romanian attests to the Slav's presence there, as well. So, if your ancestors were in any Balkan country besides Greece in CE 500, they had ancestors in Southern Russia and Ukraine in CE 1.
Seventh century Bulgar invasions: During the fourth century, the Bulgars - a nation from Western Siberia, settled in the southern Ukraine, eventually founding a state during the early seventh century. When that state was destroyed by the Khazars in the last seventh century, one group of Bulgars migrated into the Southeastern Balkans (modern Romania and Bulgaria) north of Greece, founding a second Bulgar "empire." Although they eventually assimilated (giving their name to modern Bulgaria) they added a good dose of Western Siberian, Southern Russian, and Ukranian genes to the region. If your ancestors were in Bulgaria or adjacent regions in CE 1000, they would have had ancestors in the Ukraine and Southern Russia in CE 500 and in Western Siberia in CE 1.
During the Renaissance, the Balkans were divided between two cosmopolitan empires:
Austria became the nucleus of the Hapsburg Empire (Later called Austria-Hungary) which included the modern Czech Republic, Slovakia, Slovenia, Hungary, Croatia, and bits of Italy. If your ancestors lived in this region in 1800 CE, their ancestors could have come from anywhere in this Empire in 1490 CE.
13th Century: Growth of the Ottoman Empire. The Ottoman Turks were a remnant of the Seljuks who ruled a small area in Northwest Anatolia which they managed to turn into the nucleus of a great empire. Genetically, the Ottomans were not like their Central Asian Seljuk forebears, having intermarried with the local Greek-speaking Anatolian population. Additionally, as the Ottomans expanded their state, they conquered portions of Anatolia and the European Balkans in pretty much equal amounts. Within their borders, people changed religion and intermarried. In 1453, they conquered the city of Constantinople (modern Istanbul). By the 17th century, they ruled a cosmopolitan Empire that encompassed Greece, Bulgaria, former Yugoslavia, Albania, Romania, Hungary, the fertile crescent and to a lesser extent, North Africa and pieces of Arabia. The Ottomans had a practice of drafting non-Muslim children into public service, raising them, and training them for the army or for high administrative posts. Because of this: