Question: Thorvald Eiriksson was the brother of an explorer who is believed to be the first known European to discover what continent?

Context paragraphs:
António de Andrade: Father António de Andrade (1580 – March 19, 1634) was a Jesuit priest and explorer from Portugal.  He entered the Society of Jesus in 1596.  From 1600 until his death in 1634 he was engaged in missionary activity in India.  Andrade was the first known European to have crossed the Himalayas and reached Tibet, establishing the first Catholic mission on Tibetan soil.

Nikolay Przhevalsky: Nikolay Mikhaylovich Przhevalsky (Russian: Никола́й Миха́йлович Пржева́льский ; April 12 [O.S. March 31] 1839 – November 1 [O.S. October 20] 1888 ) was a Russian geographer of Polish origin and a renowned explorer of Central and East Asia.  Although he never reached his ultimate goal, the holy city of Lhasa in Tibet, he traveled through regions then unknown to the West, such as northern Tibet (modern Tibet Autonomous Region), Amdo (now Qinghai) and Dzungaria (now northern Xinjiang).  He contributed significantly to European knowledge of Central Asia and was the first known European to describe the only extant species of wild horse, which is named after him: Przewalski's horse.

Battle of Vinland (1003): Thorvald Eiriksson had the first contact with the native population which would come to be known as the "skrælings".  After capturing and killing eight of the natives, they were attacked at their beached ships, which they defended:

Jacques de Noyon: Jacques de Noyon (1668 – 1745) was a French Canadian explorer and coureur des bois.  He is the first known European to visit the Boundary Waters region west of Lake Superior.

Juan Ponce de León: Juan Ponce de León (] ; 1474 – July 1521) was a Spanish explorer and "conquistador".  He became the first Governor of Puerto Rico by appointment of the Spanish crown.  He led the first known European expedition to "La Florida", which he named during his first voyage to the area in 1513.  Though in popular culture, he was supposedly searching for the Fountain of Youth, there is no contemporary evidence to support the story, which is likely a myth.

Abel Tasman: Abel Janszoon Tasman (] ; 1603 – 10 October 1659) was a Dutch seafarer, explorer, and merchant, best known for his voyages of 1642 and 1644 in the service of the Dutch East India Company (VOC).  He was the first known European explorer to reach the islands of Van Diemen's Land (now Tasmania) and New Zealand, and to sight the Fiji islands.

Bjarni Herjólfsson: Bjarni Herjólfsson (fl.  10th century) was a Norse-Icelandic explorer who is believed to be the first known European discoverer of the mainland of the Americas, which he sighted in 986.

Thorvald Eiriksson: Thorvald Eiriksson (Old Norse: "Þōrvaldr Eirikssonr" ; Icelandic: "Þorvaldur Eiríksson" ) was the son of Erik the Red and brother of Leif Erikson.

Leif Erikson: Leif Erikson or Leif Ericson (Old Norse: "Leifr Eiríksson" ; Icelandic: "Leifur Eiríksson"; Norwegian: "Leiv Eiriksson" 970 – c. 1020) was a Norse explorer from Iceland.  He was the first known European to have discovered continental North America (excluding Greenland), before Christopher Columbus (or possibly Saint Brendan).  According to the Sagas of Icelanders, he established a Norse settlement at Vinland, tentatively identified with the Norse L'Anse aux Meadows on the northern tip of Newfoundland in modern-day Canada.  Later archaeological evidence suggests that Vinland may have been the areas around the Gulf of St. Lawrence and that the L'Anse aux Meadows site was a ship repair station.

Pierre-Charles Le Sueur: Pierre-Charles Le Sueur (c. 1657, Artois, France – 17 July 1704, Havana, Cuba) was a French fur trader and explorer in North America, recognized as the first known European to explore the Minnesota River valley.

Supporting paragraphs: Thorvald Eiriksson Leif Erikson
Answer: North America