Sebastian Rank is a character in the Briarverse.
Sebastian Rank is the son of Martin and Isabella Rank. After an incident involving an Ackerly Green book at the local library wiped his memory of Martin, he grew up literally unable to see or remember anything relating to his father. After his mother left Martin and re-married, he had an otherwise normal childhood, grew up and got married, and had two little girls. After the Day of Change lifted whatever magic had been placed on him, he was able to reunite with his father and begin having a relationship with him again—a relationship Martin was reluctant to jeopardize by becoming involved with magic again, as he told the Mountaineers in his Neithercourier letter.