Charlemagne was King of the Franks and, after the year 800, also crowned "emperor" by the Pope in Rome. He was a Frank of the Carolingian dynasty. The Franks were a tribe of Germanic warriors who migrated into what his now called France in the 300s-400s and conquered the whole region.
The Vikings were Scandinavian warriors who launched widespread naval raids on the coasts and rivers of Europe beginning in the late 700s. They were only distantly related by language-group to the ancient Germans (which is why Scandinavian and German languages today are only slightly similar). By the late 800s, Viking raids grew so large in size that that constituted armies capable of taking over whole regions.
One powerful Viking force from the Denmark coast invaded the northern French coast, which had previously been ruled by the King of the Franks (a descendent of Charlemagne). When the Frankish king realized he didn't have sufficient strength to beat back the Vikings, he instead offered the land to them to settle and rule in his name in return for converting to Christianity and pledging loyalty to him. The early French name given to these Vikings was "Norman" ('northmen') and their province was renamed "Normandie" (Normandy) after them. Within a generation, the Viking Normans had completely christianized and assimilated into the evolving 'French' culture and language. By the time of William the Conqueror in 1066, the Normans were entirely French culturally and linguistically with virtually no remaining traces of their Viking origins.
So no, Charlemagne was not directly related to the Vikings. In fact, Vikings only showed up on the shores of his empire beginning in the last couple decades of his life.