The Elder Scrolls V: Skyrim depicts the rise of the Last Dragonborn, a legendary figure in Nordic folklore, but the game's character creation makes it so the player doesn't have to be a Nord. As the predominant race in the province of Skyrim, Nords and their culture are central to the fifth Elder Scrolls game, and venerated Nordic heroes would indeed play a pivotal role in defeating Alduin following his return in the Fourth Era. The Last Dragonborn, however, does not need to be a Nord, as evidenced by the history of the Dragonborn and how that distinction is bestowed upon individuals.
As the title of the Last Dragonborn implies, the player character in Skyrim is not entirely unique. Main villain of the Dragonborn DLC, Miraak the Dragon Priest, is the earliest known Dragonborn, and there have been many others in the history of Tamriel. Miraak was a Nord, but other notable Dragonborn, such as Saint Alessia the Slave Queen, Reman Cyrodiil, Tiber Septim, Martin Septim, and Mankar Camoran, were all of different races. Alessia was a Nede, a race from Tamriel's Merethic Era that gave way to Imperials after the Nedic population bred with Atmorans, another bygone race of humans. Reman and Martin were Imperials (Tiber's race is disputed), and Mankar Camoran was an Altmer.
Becoming a Dragonborn seemingly has nothing to do with race, although the distinction tends to follow bloodlines. Alessia was christened a Dragonborn by Akatosh, the Dragon God of Time, who gave the Slave Queen the Amulet of Kings. This powerful relic was used by many powerful lineages, including The Elder Scrolls' Septim Dynasty, to light the Dragonfires, which protect Nirn, the mortal plane, from the Daedric legions of Oblivion. The Amulet of Kings can only be worn by those who possess the blood or soul of a dragon, one of the major indicators that Mankar Camoran, leader of Oblivion's villainous Mythic Dawn cult, was secretly Dragonborn.
It's Unclear How The Player Character In Skyrim Is Dragonborn
With Martin Septim's destruction of the Amulet of Kings prior to his battle against Mehrunes Dagon at the end of Oblivion, the lineage of Dragonborn emperors comes to an end. Important occurrences from the first three games and the end of the Dragonborn rulers are the antecedent events in the prophecy of the Last Dragonborn, which foretells the return of Alduin the World Eater. It is possible that the prophecy originated from the actual, mysterious relics called the Elder Scrolls, although this is unconfirmed, according to The Book of the Dragonborn, a tome in Skyrim. Some believe the Elder Scrolls to have been created by the Eight Divines (now the Nine Divines after Tiber Septim ascended to godhood as Talos), meaning the player's character in Skyrim could be divinely inspired to thwart Alduin.
Even though this isn't a very thorough or satisfying explanation, practically random divine intervention seems the most probable explanation for how the Last Dragonborn was chosen. The inevitable return of the World Eater has long been feared, and the prophecy was even depicted in Alduin's Wall, a relief carved by Emperor Reman II's Akaviri Dragonguard in the First Era, long before any of the antecedent events took place in the Elder Scrolls games where Akaviri don't even appear. With the only prerequisite of becoming Dragonborn apparently being a blessing from Akatosh, the responsibilities of the Last Dragonborn could have conceivably fallen on anyone in or around Skyrim at the time of the Dragon Crisis. The Last Dragonborn being a Nord is certainly poetic in consideration of the province's culture, but Skyrim and The Elder Scrolls at large show that the race of Tamriel's most venerated heroes is usually inconsequential.