Sebastian got into fights a lot as a teenager. He had a smart mouth that got him in a ton of trouble, so Severin took it upon himself to first teach himself to know how to fight, and then passed those skills onto Sebastian. And that was perhaps the best thing to happen to Sebastian. 

He would win every fight he got himself into, but would still get more bruised. He was able to hide them fast before his father could notice. But one day, a black eye was harder to hide.

When asked about it, the young teen answering truthfully. His tone was prideful...he finally found something he could do that made himself feel pride over himself.

But the disappointing look and sigh from his father deflated Sebastian for the rest of the day. Well, until Severin reminded his brother that while their bästard father wasn't proud, that the older brother was extremely proud.