Daeron II Targaryen

Daeron II Targaryen, also called Daeron the Good, is an unseen character in Game of Thrones. He is not expected to appear in the series, being long dead by the time it begins.

Daeron was the second King of his name to sit on the Iron Throne and the twelfth king of the Targaryen dynasty to rule the Seven Kingdoms. He was an ancestor of Viserys and Daenerys Targaryen. He was formally styled Daeron of House Targaryen, the Second of His Name, King of the Andals and the First Men, Lord of the Seven Kingdoms and Protector of the Realm.

Background
Daeron was the son of King Aegon IV Targaryen and Queen Naerys Targaryen, born on the year 159 since Aegon's Landing. He had a sister, Daenerys Targaryen. He also had a half-brother, Daemon Blackfyre, born of the affair between his father and Queen Daena Targaryen, the sister-wife of Baelor I Targaryen.

He married Myriah of House Martell at Sunspear. With her, he fathered several sons: Baelor, Aerys, Rhaegel, and Maekar; and one daughter, Aelinor.

During his reign, his half-brother Daemon rebelled against his rule to claim the Iron Throne for himself. Daeron perished during the Great Spring Sickness. He was succeeded by his son Aerys

Season 1
Daeron II, along with siblings and progenie, is mentioned in the House Targaryen's entry of the book The Lineage and Histories of the Great Houses of the Seven Kingdoms

In the books
In the A Song of Ice and Fire novels, Daeron II was a dignified man. He had a kind thoughtful face. He was round-shouldered, with thin legs and a small pot belly. His face has a certain quiet strength, though, and his eyes are clear and full of resolve. He wore his father's elaborate dragon Crown. On his coinage, he was depicted as clean-shaven. He was not a warrior by any means, but a cultured, scholarly man who kept company with maesters and other learned men, which was one of the reasons several, more military-minded lords flocked to Daemon and supported in his failed rebellion.