Alysanne is a cousin of the ruling line of Velaryons on Driftmark. As became custom during the Long Night, she was wed to Vaemond Velaryon in order to keep their bloodline pure; a particular interest of the former Lord Varys Velaryon.
During the Targaryen Rebellion, Alysanne remained at High Tide with Lord Varys and other members of the Driftmark court. She and the maester of High Tide were with Lord Varys when he passed.
Like her husband, Alysanne was quick to support the Blackfyres following Varys' death. Some believe she may have had a hand in ending her father-in-law's life, but nothing was ever proven and his death was ruled due to his gout affliction.
Alysanne vehemently disagreed with Lord Vaemond when he chose to send two of their three sons away in 394 AC.