The Sad Tale of the Grossbart Brothers - Skellige
Quest Giver: Djenge Frett
Other Requirements: N/A
This quest begins by speaking with Djenge Frett in the town of Blandare on Skellige. He'll ask you if you've ever come across the Grossbart Brothers and fill you in on the sorts of criminals they are. After the dialogue with him ends The Sad Tale of the Grossbart Brothers Quest is added to your log.
If you've already killed the brothers then Djenge will give you half the bounty and ask you to point him to where the bodies are, the quest will conclude here. Assuming you haven't found the brothers yet, you'll find them in the fart southeastern portion of Ard Skellige, the island you're on. You'll have to ride a boat around the land mass and down to the area you see marked Grotto on my map below.
Djenge Frett will meet you at the Grotto if you spoke to him in Blandare before heading down here. He will be waiting for you just inside of the cave and will talk to you as you run by him, asking you to help him. If you choose not to help him you'll fail the quest, if he dies while you're helping him you will also fail the quest. Getting to far away from him works the same way, quest failure.
The quest completes after defeating all three of the brothers.
Note: You can find the crafting recipe for Enhanced Ursuine Armor inside of this cave - search all of the chests in the room with the Grossbart Brothers.