Father:
Hathelin son of Hamelin, called the "Far-sighted", was more bard than Ranger of the North. An average swordsman and sadly deficient archer, he was never known for his martial prowess amongst his people, despite inheriting his familial blade, the storied Valrion (of which he seemed to actively attempt to find as little usage as possible).
A decedent of a lesser noble family uplifted in the days of ancient Arnor, he treated his supposed standing with disregard and irreverence, believing them to be artifacts of the distant past and no longer meaning much.
However, Hathelin proved invaluable to his people due to his blood and the cause of his line's nobility from ages past: prophecy, truth-saying, visions of what were, could be, and are. With this gift, he discerned enemy movements before they were made, understood threats and opportunities before they ever presented themselves.
Before wedding his wife, he had a fearsome reputation as a prodigal lover, charming his way into bedding lasses all over Eriador. He also had a reputation as a tall-talker and tale-spinner. He loved the stories and histories of the world more than he loved any woman (save one), any object, any fortune.
After his marriage, an arranged affair entirely, to a cold woman of war and the wild and a definitive "she-Ranger", he became morose for a long period of time. Theirs was a loveless match for many years, both more annoyed by one another than any ill-fortune of raging weather. Until it was not.
His fiercely cold wife tempered him into a more thoughtful and wise creature, albeit with a streak of light-heartedness that was simply integral to his nature until the day he died.
Mother:
Acthellia, Daughter of Acillidoras was in everyway what one would expect from a Ranger, and a scion of kings. High-minded and haughty, her ancestral ties descended in a direct female line from Acelavali, daughter of Araval, 13th King of Arthedain. She made certain that few forgot that fact.
In no way content to be a "wilting flower" or "mere brood-mare", she dedicated herself early in life to living as men might. She fought, hunted and killed as a Ranger of the North, and became known among her people as one of their foremost captains with a bow.
Dark of hair, pale of skin and beautiful, she refused all advances for the first sixty years of her life, dedicating herself to kingly pursuits. She spent as much time with the Elves of Rivendell as not, educating herself exhaustively in the valley that held the last homely house before the sea.
When she at last (at the insistence of her chieftain) set her eye to marriage, she waxed cold as was her wont, finding faults in most, from intractable idiocy to pedantic tom-foolery, but the foremost requirement was proven noble blood of Arnor. It truly did not matter that most Rangers could claim kinship with some king or another in the long history of the Dunedain; she required a documented lineage.
When complaint was raised that no such candidate existed that fulfilled her requirements, she allowed for adherence to only the last. She believed this would avail her well, knowing one of the only proven lines was Isildur's, but Arathorn was wise in the ways of his people. He arranged her marriage to Hathelin, line of Elion.
Initially infuriated but doing her duty, theirs was a loveless match for decades until at last, it bloomed true, now dead Arathorn's wisdom reaching from the grave to give truth to their union.
When her only child was born, she changed further, becoming doting to him in ways she was never in life to anyone else, but also the instiller of duty and legacy. And it was so, until the day she died.

