Donald Tarly
Donald Tarly headed House Tarly and ruled Horn Hill during the reign of Viserys I Targaryen. His marriage to Jeyne Rowan joined two houses of the Reach, and when the realm split apart in the Dance of the Dragons, both families threw their weight behind the same claimant to the Iron Throne.
Chapter 1
The lord of Horn Hill
Books only
Donald Tarly rose to become lord of Horn Hill and head of House Tarly, while Viserys I Targaryen sat the Iron Throne.
He married Jeyne Rowan, of House Rowan of Goldengrove, and had two daughters with her: Samantha and Sansara.
Chapter 2
The Dance of the Dragons
Books only
When the realm split between supporters of Rhaenyra Targaryen and her rivals, House Tarly of Horn Hill and House Rowan of Goldengrove stood on the same side: Rhaenyra's. Donald then held Horn Hill, and his house was bound to that cause just as his wife's family was.
By the time the civil war ended, Alan Tarly held the lordship of Horn Hill, which places Donald's death before that point. It has been suggested that Alan may have been his son, though this is not certain.