was Lyanna married? to who?
She was betrothed to Robert, but Rhaegar (who was already married at that time to Elia Martel, the Red Viper's sister) supposedly kidnapped her. Whether they had a consensual affair or not has not been made clear, but she was in the tower protected by Kingsguard because Rhaegar was the crown prince and he ordered them to protect the tower.
The entire war Robert and Ned started to overthrow Aerys was partly instigated because of the kidnapping. Robert wanted his bride back, and Ned wanted his sister back.