As the oldest son of
Bjorn Ironside
Yes, Ragnar and Lagertha's son/their only surviving child dies in Episode 11 (“King of Kings”) of Season 6 (full recap here). A dying Bjorn leads the charge for Norway to defeat the Rus after several life-ending arrows get shot at him by a Rus soldier.
Ragnar Lothbrok's eldest two sons, Agnar and Eric, were allegedly killed in an attempt to make Sweden submit to Ragnar's rule. These two sons may or may not have existed; they only exist in one of the sagas discussing the life of Ragnar Lothbrok. Eric and Agnar sailed to Sweden and ordered surrender.
Ivar The Boneless
He had to work harder than the rest of Ragnar's sons to become the powerful man he was but when he finally learned, he became the best.
Of the seven grandchildren Ragnar had, then, only one is still living and recognized as part of his family line at the end of the series: Torvi and Ubbe's son, also named Ragnar. The only one of Torvi's children who survives, Ragnar is still a baby in the final episodes of the show.
As the oldest son of Ragnar and the only surviving child of Ragnar and the famous shield-maiden Lagertha, Bjorn already has the makings of a great warrior. Both of his parents are well-known for their actions during battle, and their leadership outside it.
Ivar remains a local king in England for a long time after, ruling from York but having no children to succeed him, 'because of the way he was: with no lust or love' (4).
Though he ended up leaving Kattegat with just Ivar by his side, star Travis Fimmel thinks everything worked out the way Ragnar wanted. "His relationship with Ivar I think it's his favorite relationship," Fimmel told IGN on a visit to Vikings' set.
No matter how brilliant a tactician Ivar the Boneless was, there's little doubt that Bjorn was a better overall fighter - it's even in his name, as he was dubbed 'Ironside' due to his seeming inability to be killed or harmed in battle.
Ivar becomes king over north-eastern England which his forefathers had owned (i.e. Ivar Vidfamne and Sigurd Ring), and he has two sons, Yngvar and Husto.
Björn (whose nickname “Ironside” originated from killing several enemies in battle without hurting himself) died in Vikings season 6 after being stabbed by Ivar with a sword.
Aslaug suggested that she and her husband wait for three nights before consummating their marriage after a long separation while he was in England raiding. However, Ragnar was passionate after such a long separation and did not heed her words. As a result, Ivar was born with weak bones.
Many historians believe that Ivar did exist and that he also lived up to his terrifying reputation. Ivar claimed to be the son of Ragnar and his wife, Aslaug.
And if his death has disappointed many fans, it's still one of the most emblematic moments of the TV series. Ivar made a surprising decision in the Vikings series finale, sacrificing himself in order to save the life of his brother Hvitserk. He is then killed by a Wessex soldier during the show's last epic battle.
Björn Ironside, according to Norse legends, was a Norse Viking chief and Swedish king. According to the 12th- and 13th-century Scandinavian histories, he was the son of notorious Viking king Ragnar Lodbrok and lived in the 9th century, between 855 and 858.
After failing to seduce Prince Aethelwulf, Queen Kwenthrith has both him and Bishop Edmund forcefully brought into her throne room. She then presents her son, Prince Magnus. When Aethelwulf points out that Magnus is a "Northern name", Kwenthrith proclaims that Magnus is the son of Ragnar.
Ragnar Lothbrok had at least seven sons. According to the historical accounts of Ragnar Lothbrok, through his first marriage, he had two sons, Agnar and Eric. Through his second marriage, he may have had five sons. Ivar the Boneless, Sigurd Snake-in-the-eye, Bjorn Ironside, Ubba, and Hvitserk.
Ivar shows his brothers that he can now stand and walk on his own feet with the help of new leg braces and a crutch.
Legends tell us that Ragnar – son of King Sigurd Hring – had three wives, the third of whom was Aslaug, who bore him sons Ivar the Boneless, Bjorn Ironside and Sigurd Snake-in-the-Eye, all three of whom would grow greater in stature and fame than he.
Ragnar used Athelstan's knowledge to better prepare for future raids, but as time passed and they got to know each other more, their bond became stronger, and Ragnar even admitted that he may have loved Athelstan more than Floki (Gustaf Skarsgård), another very close friend of his.
Taking into account that he had five sons and they were all grown-up by the time he died, many fans have calculated Ragnar was in his mid-fifties early-sixties when he was thrown into the pit of snakes, which is more believable than him being in his 80s.
Lagertha becomes Ragnar's prize, and in their subsequent marriage, they have two unnamed daughters as well as a son, Fridleif.
She also helps them to overthrow Oleg so that Igor can take his rightful place as heir. At the celebration feast following the defeat of Oleg, Katia informs Ivar that she is carrying his child.
Bjorn's classic moniker was derived from the belief that he was rarely wounded in battle, in fact, it was thought that he was invulnerable to any wound. The largest mound on the island of Munsö located in lake Mälaren is said to be the final resting place of this legendary Viking.
It was also heartwarming to have one final link to the original cast in the final episodes, as Vikings' Floki remained one of the last left alive. Surely, Floki dying in a cave next to a Christian cross wouldn't have done justice to the character, and the ending Hirst came up with for him was a lot more satisfying.