Complex sentence: A child of Jira, who became a concubine of the King of Aran, she had been stolen as a baby by the previous Queen Ariana who had become mentally unstable from the loss of her son to her daughter who later became Queen Eleanor.
Split into simpler sentences: A child of Jira, who became a concubine of the King of Aran. Lena had been stolen as a baby by the previous Queen Ariana who had become mentally unstable from the loss of her son to her daughter who later became Queen Eleanor.