The Dragonborn are a race of people that existed in Tails Gets Trolled.
It is unknown exactly how many Dragonborn existed within Tails Gets Trolled, but Troll King does state that they were all wiped out by The Trolls, with two exceptions - the Man in the Ice and Rob, who was previously unknown to be one until he reveals his powers as Silver's group escapes from Troll King's forces.
The Dragonborn appear to be very powerful. The Man frozen in ice by Troll King is said to be as powerful as the King himself, and is shown wielding a sword in Pacman's flashback. Rob also displays many abilities that are learned by Dragonborn within the Elder Scrolls series.
Real Life Origins
The Dragonborn are individuals from the Elder Scrolls series who are born with the blood and soul of a dragon but the form of a mortal. They are said to be extremely rare, and it is not common for more than one Dragonborn to exist at the same time. By absorbing a dragon's soul, they can learn its powers and gain knowledge.