A/N: My chat with the lovely Winterflury67 inspired this oneshot.

The horn. Heather's horn.

It had his father's seal on it.

His father, Stoick the Vast.

But Heather had specifically said that her father gave it to her. It was the only thing she remembered and had left of him.

Hiccup's fists curled at the possibilities suddenly swarming through his mind.

Was his whole life a lie? Had his father kept him in the dark for all these years?

Hiccup could not wait a moment longer. He immediately climbed on top of Toothless, the horn still in his hold, and set course straight for Berk.

He needed to confront his father for once.

-;-

It had never dawned to him how similar he and Heather looked in appearance, or even talked and behaved. Albeit Heather's recent developments, meeting her was almost like looking into a mirror. If he had left Berk three years ago, maybe this is how he would have wound up.

Hiccup had also often felt protective of Heather in a brotherly way. Now that he realized she might be family, everything suddenly made perfect sense.

But it also broke his heart.

He would now always be left wondering how it would have been to grow up alongside her. Whether it would have affected his fated rendezvous with Toothless, or any of the major occurrences that have happened in his life. Would things have been different then?

The next question that popped into his mind was; why?

If Heather was indeed his sister, then why was he just finding that out now?

Why had his parents given up on their own daughter?

Hiccup let out a humorless laugh, his own insecurities staring back at him.

The whole ride was filled with uneasiness, shock and silent rage. But underneath it all, there was also a small bundle of joy prickling his heart.

He might have a sister, and the idea did not sound half as bad as he initially thought.

-;-

"Dad, is Heather my sister?" Hiccup asked in a small voice, bringing the horn forward for inspection.

Stoick stared at his son with wide eyes before relaxing slightly as he considered his response carefully. After a moment of hesitation he motioned toward his son to take a seat by the great table.

Hiccup listened intently as his father explained the truth behind the horn.

Stoick pretended not to notice the disappointment washing over his son's face as he revealed parts of the past. He knew what his son must have been thinking when he first arrived here. But there were certain things that were best left in the dark for everyone's sake.

What was important for Hiccup to know was that Heather belonged with the Beserker tribe, and that she was Oswald the Agreeable's daughter.

Stoick deliberately left out the part about the Berserker bloodline running through Hiccup's own veins.

After all, what was the point of burdening the boy with such minor details?

Oswald the Agreeable was dead.

And as was Oswald's sister.

Valka.

A/N: I will stand by this headcanon until proven wrong. There are too many similarities between Valka and Heather, not to mention how Valka possesses many traits of a Beserker. We also know Stoick and Valka's marriage was arranged since Valka is 10 years younger than him. This theory makes sense and it does not take anything away from canon since it doesn't directly interfere with Hiccup's character.

To the anon reviewer: No. Valka is not Spitelout's sister. Nowhere in canon does it say that. That is just one fan's theory. It is no more legitimate than my headcanon. I have actually heard that most fans believe Spitelout to be from Stoick's side of the family. It's also possible Spitelout is not related to any of them. So don't come here and tell me I'm wrong when your own arguments are completely baseless and removed from canon.