The Lost Brother Walkthrough
At the beginning of the fourth chapter, The Varnhold Vanishing, Lord Hanvaki arrives to your throne room. He will ask you to find his missing brother — Tomin Hanvaki. Head to the Varnhold and discover a place called Shallow Gulch.
Go there, complete the text quest and find the body of Tomin. Return to the capital and talk to his brother again — he should be in the tavern.
Now you need to discover the fate of Hanvaki’s great-grandfather. You will find the quest letter in one of the rooms in the Sepulchre of Forgotten Heroes. No worries, you will visit the location during The Lost Relic quest anyway. Do not sell the letter. Go back to the tavern and show it to Edrist to complete your objective and earn 750 experience points.
Varnhold Vanishing is the 3rd chapter, not the 4th. Both Troll Trouble and Season of Bloom are chapter 2.