Ukraine is once again at the center of European discussion. On April 6,  in a nonbinding referendum, Dutch citizens voted by 61 percent to reject the E.U.-Ukraine Association Agreement. All 27 other E.U. members already have approved it.

This is the same agreement that sparked protests and upheaval throughout Ukraine in November 2013, when then-President Viktor Yanukovych refused to sign it. In June 2014, newly elected President Petro Poroshenko signed the agreement, heralding Ukraine’s first step towards full E.U. membership. The Dutch parliament approved the association agreement in 2015, but this vote was triggered by a petition sponsored by Euroskeptics and was widely seen by them as a referendum on the E.U., not about Ukraine. However, for Ukrainians, this signals that Ukraine is not wanted as part of Europe — and that Europe does not support Ukraine’s precarious geopolitical position.

To understand present-day Europe and put these arguments in context, you need to understand European history. A look at medieval maps and family trees reveals that Ukraine has always been part of Europe.

Let’s look at the history of Ukraine

The research for my book “Reimagining Europe” shows that modern-day Ukraine was squarely in the middle of the largest kingdom in medieval Europe, particularly in the 11th and 12th centuries. The medieval kingdom of Rus’ was the predecessor of the modern states of Ukraine, Russia and Belarus. Rus’, based at the current Ukrainian capital of Kiev, stretched to the Baltic in the north and the Black Sea in the south, to Poland and Hungary in the west and eastward toward the Urals.

The ruling family (known as Volodimerovichi or Riurikids) were involved in the medieval European system of dynastic marriages. For instance, the Rusian princess Anna married Henri I of France, and bore his son and heir Philip, the first with that name, in the middle of the 11th century. Anna’s sister married an exiled Anglo-Saxon king of England; and her niece was the German empress.

In fact, more than 70 percent of the Rusian royal marriages linked the Rus’ kingdom to Europe’s other ruling families. The Harvard Ukrainian Research Institute’s interactive, online map of these marriages shows a tight web of connections throughout Europe, all tied to the Rusian royal family.

Tracing the connections

The first thing that jumps out from the map is that these marriages define the boundaries of Europe. They begin in cities throughout Europe and link all the royal families that made up the medieval European world.

My recent book “Ties of Kinship” illustrates how women from Rus’ became queens of France, Poland, Hungary, Norway, Denmark and the German Empire. One story in particular demonstrates this interconnection. In the middle of the 12th century, two sisters from Rus’ married into the Norwegian and Danish royal families. In Denmark, Ingeborg married Knud Lavard, who was later murdered. Their son was named Valdemar after Ingeborg’s grandfather, Volodimer Monomakh, the ruler of Rus’.

However, Valdemar had a difficult time ascending to the Danish throne, in part because of his father’s murder. His mother and his aunt Malfrid, the queen of Norway, intervened, and Valdemar eventually was crowned. Valdemar went on to become one of the most powerful Danish kings. That was possible only because of two Rusian women, who – like so many from Rus’ — were active parts of the kinship web that shaped Europe.

The kingdom of Rus’ began to come apart in the 13th century because of divisions within and invasions from without. But Rus’s westerm portions, which eventually become Ukraine, stayed firmly connected to Europe. The territories known as Galicia and Volhynia had intermittently powerful local rulers — and were enmeshed in Hungarian and Polish politics.

The best example is Daniil Romanovich, whose father, the ruler of Galicia and Volhynia, died when Daniil was just a boy. Daniil was raised at the court of Andrew II, the king of Hungary, and throughout his youth, Andrew, Leszek the White of Poland, and Galician nobleman all contested for the opportunity to put Daniil on his father’s throne. Once he did get back on the throne, Daniil had to contest with those same powers to maintain his independence. When the Mongols invaded, Daniil submitted to them, but also maintained ties to the larger European world. He married one son to the granddaughter of Andrew II of Hungary and another son to the niece of Emperor Frederick II of the German Empire; in addition to receiving a crown from the Pope Alexander IV.

The region’s rulers and nobles continued to intermarry throughout Europe – and the rivalries continued as well. Following Daniil’s death, the Hungarian kings even claimed the title, ruler of Rus’ for many years due to their association with him. The Poles, Lithuanians, Hungarians, Mongols and others all contested over this land, wanting to have it as part of their growing realms.

What it all means

In other words, medieval history shows that Ukraine has long been part of Europe, connected by trade, religion, alliances and marriage. Though some have argued that Ukraine is not part of Europe (generally equating “the West” with Europe and opposing it to Russia), this is a historically fallacious claim.  They are certainly free to claim that Ukraine’s democracy, politics or economy aren’t worthy of the Association Agreement, or that the agreement will be bad for either the European Union or Ukraine, or both.

But to argue that Ukraine is not and has not been part and parcel of Europe is just wrong.

Christian Raffensperger is associate professor at Wittenberg University as well as an associate of the Harvard Ukrainian Research Institute. He is the author of “Reimagining Europe: Kievan Rus’ in the Medieval World and Ties of Kinship: Genealogy and Dynastic Marriage in Kyivan Rus’.”