Guilbert is first encountered during the quest "Separated at Birth," when his brother Reynald Jemane in Chorrol hires the Hero to find out who is impersonating him in Cheydinhal. Upon learning that his brother, whom he believed to be dead along with his mother after their childhood home was sacked by Ogres, still lives, he leaves for Chorrol immediately. Upon arriving in Chorrol, he will meet his brother at The Grey Mare and from then on, Reynald will always refer the Hero to Guilbert.
After he is reunited with his brother, Guilbert will give the quest "Legacy Lost," asking the Hero to scout out the location of their childhood home, Weatherleah, and defeat any Ogres that are still inhabiting the property. Upon doing so, he will ask the player to escort him and his brother there so that they can rebuild.
After escorting the twins to Weatherleah, the Hero will be approached by Fathis Ules, who will tell them that Albert Jemane, their father, was a thief who was part of the Thieves Guild. Ules will ask them to retrieve an item which Albert stole (and subsequently lost to the Ogres when Weatherleah was sacked) and never handed in. When confronted about this, Guilbert will deny Ules' claims, saying that his father was an honorable man.
- Guilbert Jemane and his brother are both marked as essential, making them useful followers should the Hero never decide to finish "Legacy Lost."
- Sometimes, when the Hero decides to fast travel back to Chorrol after meeting Guilbert in Cheydinhal during "Separated at Birth," they must wait a day for him to catch up.