Rhaegel Targaryen

Rhaegel 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 Rhaegel was the third son of King Daeron II Targaryen and Queen Myriah Martell. He was the brother of Baelor "Breakspear", Aerys, Maekar and Aelinor.

Season 1
Prince Rhaegel, along with his family, 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, Prince Rhaegel was the third son of King Daeron the Good and Queen Myriah. He was sickly, meek, and mad. He was known for dancing naked through the halls of the Red Keep. He also fathered twins.

After his elder brother, King Aerys, died without issue, Rhaegel's children were passed over in the succession, as it was feared they would inherit their father's madness. Instead Maekar was named King.