The former ruling house of the Seven Kingdoms from the capital city of King's Landing. Also known as the Dragon Kings, because they used to ride dragons and had a strange bond with them. They came from the eastern continent of Essos and under the historical leadership of Aegon The Conqueror, they unified Westeros with their dragons as weapons and ruled there for 300 years. They often married brother to sister throughout their rule despite the laws of their religion, which probably accounts for their history of mental instability among the later rulers. Their rule ended when Robert Baratheon overthrew Aerys II Targaryen and his surviving children fled into exile in the Free Cities. Their sigil is a three-headed dragon and their members have silver hair and purple eyes.
House Targaryen was one of the ancient noble houses known as dragonlords who ruled the Valyrian Freehold, a great empire spanning most of the eastern continent. They were traditionally not one of the most important of these families, however. When they had predicted that a cataclysm would come over Valyria, only the Targaryens heeded their vision and fled to the westernmost outpost of Valyrian influence, the island of Dragonstone, off the east coast of Westeros. Twelve years later the Doom descended on the city of Valyria, leading to the collapse of the Freehold. The Targaryens were one of the few families to survive the destruction of their home and were the only dragonriders of Valyria to survive.
Following the Doom, however, the Targaryens remained on Dragonstone for another century. When the young Aegon the Conqueror developed ambitions toward Westeros. He aspired to unite the seven Westerosi kingdoms under one ruler, himself. A hundred years after the Doom, Aegon set forth from Dragonstone with his sister/wives Rhaenys and Visenya, their dragons, and a small force, landing at the mouth of the Blackwater Rush and beginning the Wars of Conquest. Those who had bent the knee to him were allowed to remain in power (such as Houses Lannister, Stark and Tyrell) as Lords Paramounts of the Seven Kindgoms. During his campaigns, Aegon was anointed king by the High Septon in Oldtown, leading to the unification of the Seven Kingdoms under Targaryen rule from the Iron Throne, starting a dynasty that lasted nearly 300 years. The area where the Targaryens began their conquest became the site of their new capital, King's Landing. Dragonstone was used as the seat of the heir to the throne. The region around these strongholds became known as the Crownlands. Another close ally was House Baratheon; Aegon had installed his bastard brother Orys Baratheon to rule the Stormlands. After extinguishing House Hoare, the Greyjoys were allowed dominion over the Iron Island while Dorne was joined through dynastic marriage after decades of resisting conquest.
The Targaryens kept dragons for much of their reign in Seven Kingdoms. To house them they built an immense domed structure in King's Landing called the Dragonpit. New dragons were bred from Aegon's original three: Vhagar, Meraxes, and the dreaded Balerion. However, violent deaths in battle and a growing infirmity in each following generation caused the family's stable to dwindle. The last Targaryen dragon was a deformed and sterile creature that died very young. It is not clearly understood what caused the last dragons to die out. A legend holds that Aegon III poisoned them, but Archmaester Marwyn suggested that the maesters were somehow responsible. Others have also claimed that raising dragons in enclosed spaces, even the Dragonpit, was unnatural and stunted their growth.
It was said that "Madness and greatness were two sides of the same coin and every time a new Targaryen was born, the gods would toss the coin in the air and the world would hold its breath to see how it would land." and true to this statement, they had as many insane rulers as great ones. This madness was likely the result of inbreeding due to marriage between brothers and sisters, some were born already mad while others may not display madness when they are younger but can develop it as the years go by, and may also skip a generation.
King Aerys II Targaryen was the last king in a dynasty which had held for nearly 300 years of unbroken rule. Where the Targaryens had begun as untouchable demigods atop fire-breathing dragons, their power had fallen noticeably since the time of those beasts, with many more large-scale civil wars featuring pitched battles. In the short term, Aerys's madness had provoked the nobles to action, but such open defiance would not have occurred if his family's prestige had not been in decline for some time.
When his son, Prince Rhaegar Targaryen, ran off with Lyanna Stark. her brother and father protested, and in response, Aerys had them executed, starting a civil war. Rhaegar took command of the royal troops, leading them to defeat in the Battle of the Trident, where he was killed by Robert Baratheon. Prince Viserys and the pregnant Queen Rhaella fled to Dragonstone. While the treacherous Lannisters had sacked King's Landing in Robert's name and Aerys was murdered by his own Kingsguard Jaime Lannister. On Dragonstone, Rhaella died giving birth to Princess Daenerys, who was spirited to the Free Cities along with Viserys by the loyal Ser Willem Darry. Robert Baratheon was crowned king, partially due to his having a Targaryen grandmother. The surviving Targaryens', Viserys and Daenerys wander through the Free Cities looking for aid in retaking the Seven Kingdoms but few take their claim seriously. Even if they are reduced to only two members after the Rebellion, Robert Baratheon still fears the Targaryens may become a problem in the future in the case they forge a powerful alliance to travel west.
The Mad King's surviving son Viserys Targaryen betroths his sister to Drogo, a mighty khal of the Dothraki, hoping to use his horde to retake the Seven Kingdoms, but Drogo has little interest in Viserys desire. Viserys alienates the horselord with his arrogance and is eventually killed. With Viserys' death, Drogo loses interest in the notion of invading Westeros, despite Dany's attempts to persuade him. This changes, however, when Ser Jorah prevents an assassin from poisoning Daenerys and discovers that Robert Baratheon has placed a price on her head. Enraged, Drogo vows before his khalasar to avenge this insult by conquering Westeros to seat his son on the Iron Throne that his mother's ancestors had once held. Drogo however dies before he could reach Westeros and Daenerys takes command of the khalasar's ragged remnants, and is able to hatch three dragon eggs, the first in a century and a half.