Lord of the Hightower|
Lord of the Port
Voice of Oldtown
Defender of the Citadel
Beacon of the South
|Born||In 115 AC|
|Spouse(s)||Lady Samantha Tarly|
|Book(s)||Fire & Blood (mentioned)|
Lyonel was born in 115 AC to Lord Ormund Hightower and his first wife, who died in childbed at some point. He had two younger brothers, Martyn and Garmund, and a sister, Bethany. During the Dance of the Dragons, his father married again to Samantha Tarly, known as "Lady Sam."
Lyonel became Lord of the Hightower at age fifteen, after his lord father was killed at the First Battle of Tumbleton. It is said that when Lord Corlys Velaryon's peace terms were first offered to Lord Lyonel, he ripped the parchment from his maester's hand and tore it to shreds, vowing to write a reply in the Sea Snake's blood. However, his step-mother had other ideas. According to Mushroom, she persuaded Lyonel to agree to the terms by allowing him to seduce her and promising to marry him if he surrendered. This was because she was related to both the Tarlys and Rowans, who supported Rhaenyra's blacks. Munkun believes that Lord Hightower accepted the terms because of the end to Tyrell neutrality, however, and his youngest brother being at Highgarden at the time. 
Lord Lyonel announced his intention to marry his father's widow, but the reigning High Septon forbade the union as a form of incest. However, Lyonel kept Samantha as his paramour for thirteen years and fathered six children on her. Lyonel and Lady Sam attended the coronation of Aegon III and his wedding to Queen Jaehaera, with their presence being so great a scandal that the High Septon refused to travel with them. 
Relations between the Hightowers and the Faith soured when the High Septon commanded Lady Sam to remove herself from her step-son's bed and take vows as a silent sister as penance. When she refused, he condemned her as a shameless fornicator and forbade her to set foot in the Starry Sept until she repented. Instead, Lyonel's wife famously confronted the High Septon, forcing him to relent.
King Aegon III planned to visit Lord Lyonel and Lady Samantha in Oldtown in a royal progress to mark his coming of age.
A new High Septon eventually reversed the position of his predecessor, allowing Lord Lyonel to marry Lady Sam.