Born around the year 25 before the Conquest, Queen Rhaenys Targaryen, daughter of Lord Aerion Targaryen and Lady Valaena Velaryon, is both the sister and wife of Aegon I Targaryen. She is the youngest of the siblings by almost two years, and much calmer and more feminine than her older sister Visenya.
Playful and curious, she loves music and poetry. She rides the mighty dragon Meraxes, and spends twice as much time on the back of the dragon as her brother and sister do. Her greatest desire is to one day fly beyond the Twilight Seas to find out what is there.
According to some sources, Rhaenys and her sister Visenya stayed with the Redwyne.
In the early days of the Conquest, Rhaenys proclaims the royal dignity of her brother Aegon at his first coronation. She then accompanies her half-brother Orys Baratheon, who marches towards the Stormlands, and can inform him about the movements of the army of King Argilac the Arrogant.
She participates in the battle of the Last Storm, where the flames of Meraxes contribute greatly to the victory. She then flies to Dorne, where she takes Vaith and Bourg-Cabanes. She reached Lancehélion, where she could not convince the old princess Meria Martell to submit.
King Aegon I Targaryen marries his two sisters after the Conquest, but he spends only one night with Visenya and ten with his sister Rhaenys. Despite her marriage, Queen Rhaenys likes to surround herself with charming young men, (and it is whispered that she sees them especially when Aegon is with Visenya).
She is the first of the two sister-wives to give birth to a son who will become the second king of the Targaryen dynasty as Aenys I Targaryen.
Although upon the death of his son Aenys, the crown passed to his sister Visenya's son, Maegor I Targaryen, the latter's death without an heir would put Aenys' son, Jaehaerys I Targaryen, on the throne, probably too young when his father died. In fact, the Targaryen dynasty originated from Queen Rhaenys Targaryen.
As King Aegon was often on royal travels, in order to meet his subjects, he regularly delegated the government of the Seven Crowns to his sister-wives and advisors. This is how Rhaenys was once led to enact the rule of the six, concerning the punishment that could be inflicted on an adulterous wife.