Of course ukrainians speak russian , but that does not mean they are russians.They speak it cause they were conquered/part of USSR for many years.
Kosovo people speak serbian , but that does not mean they are serbians.They speak it cause they were conquered by Serbia and were part of Yugoslavia.
These two cases doesn't have much in common. Kosovo was not conquered. That is a region, which was serbian, like forever... In last century or so, many albanians moved to that region and they become majority, so they simply decided not to be part of Serbia anymore and declared independence. Of course, with most of the "big boys", "protecting their back"...