Baelor Targaryen (son of Daeron II)

"Once in a long while, you may get two real highborn shits having a go at each other and one of them might be fool enough to demand a trial by seven. Exactly how it sounds: seven men against seven men. Makes for a good show, but any man who has been in battle knows that the more men involved, the less skill needed, the more chance of accidents. Just ask that Targaryen prince who got his head staved in by his brother all those years ago, and all for some hedge knight."

- Bronn

Baelor Targaryen 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.

Background
Prince Baelor was the eldest son of King Daeron II Targaryen and Queen Myriah Martell. He was the brother of Aerys, Rhaegel, Maekar and Aelinor.

He was killed when his brother Maekar staved his head in during the Trial by seven of Duncan the Tall.

Season 1
Prince Baelor, along with his family, is mentioned in House Targaryen's entry of the book The Lineages and Histories of the Great Houses of the Seven Kingdoms.

In the books
In the A Song of Ice and Fire novels, Prince Baelor was the eldest son of King Daeron the Good and Queen Myriah, and named after Baelor I. He had the dark hair of his mother, Queen Myriah, which he kept it cut short and kept his jaw clean-shaven. His nose had been broken twice. He was known as "Baelor Breakspear" and was the father of Princes Valarr and Matarys Targaryen.

When the Blackfyre Rebellion was in its early stages, Prince Baelor advocated leniency toward Daemon Blackfyre, a position that was rejected in favor of his uncle Brynden Rivers' hard line. Nonetheless, Baelor accepted the path towards war and distinguished himself by leading the Dornish-Stormlands force which attacked the rearguard of the rebel army during the Battle of Redgrass Field, smashing them against the shield-wall of his brother, Prince Maekar, and inspiring the song The Hammer and Anvil. After the battle, he was named Hand of the King by his father. At some point he was also given the title of Protector of the Realm.

While participating in a rare seven versus seven man variant of a Trial by combat, Baelor's younger brother Maekar accidentally dealt him a severe blow to the head with his mace. Baelor had entered the trial wearing his son's lighter armor, which did not fit properly and didn't provide adequate protection. Maekar had not meant to severely harm Baelor, and Baelor seemed fine at first, acknowledging that it was an accident. Soon, however, Baelor started behaving drunkenly, and he actually had a severe concussion from which he died in a matter of hours. The guilt of accidentally killing his own brother haunted Maekar for the rest of his days.

When he died his son Valarr became heir-apparent to the Iron Throne, but he and his younger brother Matarys both died during Great Spring Sickness only hours before Daeron II. This lead Daeron II to be succeeded by his second son, Aerys I.