"I'm rusich", - so could say about itself any habitant of Kyivan Rus'
In the 8th century, the territory of Kyivan Rus’ was inhabited by a number of tribes who shared a common proto-Slavic language, pagan beliefs, and life-style. The ancestors of the Ukrainians included the Polianians, Siverianians, Derevlianians, Dulibians, White Croatians, Ulychians, and Tivertsians. The proto-Russian Krivichians, Viatichians, and Radimichians and the proto-Belorussian Drehovichians also lived on the lands that eventually constituted Kyivan Rus’. The Polianians were the largest and most developed of the tribes; according to the Rus’ Primary Chronicle, their prince Kyi founded the city of Kyiv in the 6th century. None of the tribes, however, was able to create a viable state, and in the 9th century the Varangians from Scandinavia conquered the tribes and laid the groundwork for the Kyivan Rus’ state.
Personally I consider that Ukraine is the heiress of Kyivan Rus', also as Italy is the heiress of the Roman Empire. The center of Kyivan Rus' was in Kyiv, but not in Moscow (Moscow then was not still present).
And Russia and Byelorussia sure have attitude toward Kyivan Rus' how its parts are, however center of Kyivan Rus', its heart was on earths of modern Ukraine.
Kyivan Rus' is not Russia. Coat of arms of grand duke of Kyiv Volodymyr the Great - golden trident is the coat of arms of modern Ukraine. And Kyiv is capital of Ukraine.
Chinks of grand duke of Kyiv Volodymyr the Great
Coat of arms of Ukraine: