Question: Danish Viking, who ruled over parts of Friesland between 841 and 873 was the uncle of a Viking leader who raided the British Isles, West Francia, Frisia, and Lotharingia in the 860s and 870?
Context: The First Viking Age in Ireland began in 795, when Vikings began carrying out hit-and-run raids on Gaelic Irish coastal settlements.  Over the following decades the raiding parties became bigger and better organized; inland settlements were targeted as well as coastal ones; and the raiders built naval encampments known as longphorts to allow them to remain in Ireland throughout the winter.  In the mid 9th century, Viking leader Turgeis or "Thorgest" founded a stronghold at Dublin, plundered Leinster and Meath, and raided other parts of Ireland.  He was killed by the High King, Máel Sechnaill mac Máele Ruanaid, which was followed by several Irish victories against the Vikings and the seizure of Dublin in 849.  Shortly after, a new group of Vikings known as the Dubgaill ("dark foreigners") came to Ireland and clashed with the earlier Viking settlers, now called the Finngaill ("fair foreigners").  The wavering fortunes of these three groups and their shifting alliances, together with the shortcomings of contemporary records and the inaccuracy of later accounts, make this period one of the most complicated and least understood in the fledgling city's history.  In 853 a Viking warlord called Amlaíb (, possibly Olaf the White) arrived and made himself king of Dublin.  He ruled along with his brothers Ímar ("Ívarr", possibly Ivar the Boneless) and Auisle ("Ásl").  For the next fifteen years or so, they used Dublin as their base for a series of campaigns against Irish kingdoms.  During these conflicts they briefly allied themselves with several Irish kings.  The Dublin Vikings also carried out a number of raids in Britain at this time.  The deaths of Ivar (c.873) and Olaf (c.874) were followed by internecine conflict among the Vikings.  Although intermittent warfare between the Vikings and the Irish continued, these inner conflicts weakened the Viking colonies and made it easier for the Irish to unite against them.  In 902, Cerball mac Muirecáin, king of Leinster, and Máel Findia mac Flannacáin, king of Brega, launched a two-pronged attack on Dublin and drove the Vikings from the city.  However, in 914 the Vikings now known as the Uí Ímair (House of Ivar) would return to Ireland, marking the beginning of the Second Viking Age. Rorik ("Roricus, Rorichus"; Old Norse "Hrørek", c. 810 – c. 880) was a Danish Viking, who ruled over parts of Friesland between 841 and 873, conquering Dorestad and Utrecht in 850.  Rorik swore allegiance to Louis the German in 873.  He died at some point between 873 and 882. Æthelflæd, Lady of the Mercians ( 870 - 12 June 918) ruled Mercia in the English Midlands from 911 until her death.  She was the eldest daughter of Alfred the Great, king of the Anglo-Saxon kingdom of Wessex, and his wife Ealhswith.  Æthelflæd was born around 870 at the height of the Viking invasions of England.  By 878 most of England was under Danish Viking rule, East Anglia and Northumbria having been conquered and Mercia partitioned between the English and the Vikings, but in that year Alfred won a crucial victory at the Battle of Edington.  Soon afterwards the English-controlled western half of Mercia came under the rule of Æthelred, Lord of the Mercians, who accepted Alfred's overlordship.  Alfred adopted the title King of the English, claiming to rule all English people not living in areas under Viking control.  In the mid-880s, Alfred sealed the strategic alliance between the surviving English kingdoms by marrying Æthelflæd to Æthelred. Godfrid, Godafrid, Gudfrid, or Gottfrid (Old Norse: "Guðfrið" ; murdered June 885) was a Danish Viking leader of the late ninth century.  He had probably been with the Great Heathen Army, descended on the continent, and became a vassal of the emperor Charles the Fat, controlling most of Frisia between 882 and 885. Norse activity in the British Isles occurred during the Early Medieval period when members of the Norse populations of Scandinavia travelled to Britain and Ireland to settle, trade or raid.  The Norse peoples who came to the British Isles have been generally referred to as Vikings, but it is a matter of debate if the term "Viking" represented all Norse settlers or just those who raided. In medieval historiography, West Francia (Latin: "Francia occidentalis") or the Kingdom of the West Franks ("regnum Francorum occidentalium") was the western part of Charlemagne's Empire, inhabited and ruled by the Germanic Franks that forms the earliest stage of the Kingdom of France, lasting from about 840 until 987.  West Francia was formed out of the division of the Carolingian Empire in 843 under the Treaty of Verdun after the death of Emperor Louis the Pious and the east–west division which "gradually hardened into the establishment of separate kingdoms (...) of what we can begin to call Germany and France." Ímar (Old Norse: "Ívarr" ; died c. 873) was a Viking leader in Ireland and Scotland in the mid-late ninth century who founded the Uí Ímair dynasty, and whose descendants would go on to dominate the Irish Sea region for several centuries.  He was the son of the king of Lochlann, identified in the non-contemporary "Fragmentary Annals of Ireland" as Gofraid.  The "Fragmentary Annals" name Auisle and Amlaíb Conung as his brothers.  Another Viking leader, Halfdan Ragnarsson, is considered by some scholars to be another brother.  The Irish Annals title Amlaíb, Ímar and Auisle "kings of the foreigners".  Modern scholars use the title "kings of Dublin" after the Viking settlement which formed the base of their power.  Some scholars consider Ímar to be identical to Ivar the Boneless, a Viking commander of the Great Heathen Army named in contemporary English sources who also appears in the Icelandic sagas as a son of the legendary Viking Ragnar Lodbrok. Frothar or Frotar (Latin "Frotharius", French "Frotaire") was an Aquitanian prelate in West Francia, who held two different bishoprics and three abbacies during a long career.  He was appointed Archbishop of Bordeaux around 859, but Viking raids forced him to abandon his seat in 870.  With papal approval, he was transferred to the archdiocese of Bourges in 876.  He died after 893. Vikings (Old English: "wicing"—"pirate", Danish and Bokmål: "vikinger" ; Swedish and Nynorsk: "vikingar" ; Icelandic: "víkingar" , from Old Norse "víkingar "), were Norse seafarers, mainly speaking the Old Norse language, who raided and traded from their Northern European homelands across wide areas of northern, central and eastern Europe, during the late 8th to late 11th centuries.  The term is also commonly extended in modern English and other vernaculars to the inhabitants of Viking home communities during what has become known as the Viking Age.  This period of Nordic military, mercantile and demographic expansion constitutes an important element in the early medieval history of Scandinavia, Estonia, the British Isles, France, Kievan Rus' and Sicily. Rodulf Haraldsson (died June 873), sometimes Rudolf, from Old Norse Hróðulfr, was a Viking leader who raided the British Isles, West Francia, Frisia, and Lotharingia in the 860s and 870s.  He was a son of Harald the Younger and thus a nephew of Rorik of Dorestad, and a relative of both Harald Klak and Godfrid Haraldsson, but he was "the black sheep of the family".  He was baptised, but under what circumstances is unknown.  His career is obscure, but similar accounts are found in the three major series of "Reichsannalen" from the period: the "Annales Bertiniani" from West Francia, the "Annales Fuldenses" from East Francia, and the "Annales Xantenses" from Middle Francia.  He died in an unsuccessful attempt to impose a danegeld on the locals of the Ostergo.
Answer: Roricus, Rorichus