Question: are cersei and jaime really brother and sister?
Answer: Queen Cersei and her twin brother Ser Jaime Lannister have continued an illicit romance since childhood. Cersei's children: Joffrey, Myrcella, and Tommen, are all born of their affair. ... This makes their children Jaime, Cersei, and Tyrion not only siblings, but second cousins to each other.