The son of Chieftain Arador of the Dúnedain, and a descendant through many generations of Isildur himself. Of Arathorn's early life, little is known. He first appears in annals at the age of fifty-six, seeking the hand of Gilraen as his wife. Gilraen at that time was just twenty-two years old, and though the wedding was at first opposed by her father Dírhael, she became Arathorn's wife.
The following year, Arathorn's father Arador was slain by trolls, and Arathorn took on the title of Chieftain of the Dúnedain. Gilraen bore him a son, who was given the name Aragorn. Aragorn would not know his father for long - when he was just two years old, Arathorn went hunting orcs, and was shot through the eye by an arrow. After Arathorn's loss, Gilraen took their son to Rivendell to be fostered by Elrond.
Arathorn II served as Chieftain of the Dúnedain for just three years. He was succeeded by his only son, who would become Chieftain Aragorn II, and in time King Elessar of the Reunited Kingdom of the Dúnedain.