Catelyn Stark's younger sister, she too was raised with Petyr Baelish (aka Littlefinger). She was married off to the much older Jon Arryn (the former Hand of the King) when Robert Baratheon led his rebellion against the Mad King.
Lysa and Jon Arryn's son, Robin lives an extremely sheltered life under the watchful eyes of his mother.
Game of Thrones Houses
Located in the Vale, the Arryns serve as Wardens of the East from their mountain stronghold, the Eyrie – a key defense against the violent clans that surround their home. The widowed Lysa Arryn retired here, keeping herself out of thr fray below. Lysa was murdered by her husband, Petyr "Littlefinger" Baelish, shortly after their wedding. Young Robin Arryn now heads the household, under Littlefinger's guidance.