"Do you really wish to know?" Spoilers from the books and/or games to follow!
Kayleigh was one of the members of the Rats. He was slender, with long blonde hair reaching to his shoulders. He was the adopted son of the castellan in Ebbing. His face was angular, his eyes a mad green, and his mouth was usually twisted into a nasty grimace. He wore earrings and had a snake tattoo. He dressed in a black calf skin with silver accents. The castle where he used to live however, was besieged by the Nilfgaardian Army by order of Emhyr var Emreis, the Emperor of Nilfgaard, in order to suppress a uprising in Ebbing. He woke up in the burning castle, among the bodies of his adopted parents. He then found Reef, a Nilfgaardian soldier whose mates left him because of his injuries. Instead of finishing him off however, Kayleigh helped and healed him. They then met Giselher, Iskra, Asse and Mistle during the holiday of Lammas and formed a gang.
Ciri first met him at the inn in Glyswen where both she and he had been dragged against their will by two different gangs: Ciri by the Trappers, and Kayleigh by the Nissir. The night of his rescue he attempts to rape Ciri, but is chased away by Mistle who takes over where he left off.