The character of Ivar the Boneless (kind of) had a son in Vikings season 5, but due to a facial deformity, the baby Baldur was left in the forest to die. ... Ivar was the youngest son of Ragnar and Queen Aslaug, and he was born with a genetic disorder known as osteogenesis imperfect, also known as brittle bone disease.

What's wrong with Ivars son in Vikings?

The shocked and saddened Ivar leaves Baldur to die at night, unknown to Freydis. It is later confirmed that his remains were found eaten by foxes. Despite not being Ivars biological son Baldur was born a cripple which made Ivar reject the child as he wanted a healthy baby.

What deformity did Ragnar's son have?

Because Ragnar did not heed her warnings, Ivar was born with weak bones, his legs twisted and seemingly broken, hence the nickname "Boneless." When he was born, Aslaug and Ragnar feared for his difficult life.