Jaime and Cersei’s romanticized idea of being one soul in two bodies is so fascinatingly destructive. So much of their relationship is based on this notion of fundamentally refusing to accept the other as a whole. Both of them want to shove the other inside of a box of their creation that is kind of antithetical to them as people. Cersei does use Jaime and her children as extensions of herself to achieve things that society keeps from her grasp due to her gender. She locks Jaime inside this box where he functions as her sword, essentially. Then the whole point of Jaime’s arc in ASoS is to establish that he is more than a sword. More than rituals of violence. To me, Jaime’s obsession with Cersei continuing past their childhood mainly stems from a tight clinging to the past. Following Jaime’s trauma, disillusionment, and increasing isolation due to his experience with Aerys and knighthood, he views the relationship as the only concrete thing in his life and relies on it for affirmation and meaning. He also uses Cersei as a means of dissociation— filling his head with thoughts of her during the executions, “losing himself in her flesh”— a way “to go away inside” during horrors. He also unconsciously never wants to move on from being that blissfully ignorant romantic boy that he was, so he desperately keeps the one thing that is constant (his twin sister - a constant from birth), and romanticizes a relationship that is not what he believes it is. He projects her onto a pedestal and obsesses over an ideal that does not exist, also putting her into the role of a perfect woman (“I thought she was The Maiden”, a fictive ideal), to create some kind of purity he can guard, in a way reflecting the expectations of the rest of society that she does not actually fit, nor does she want to. He puts himself in the position of a knightly protector figure to cope with his own identity crisis and the destruction of his self concept. He needs her in order to feel needed. They need each other for self-love. But both of them also dehumanize the other in different ways, and to different extents. “You are my other half” is a twisted notion that prevents the autonomy and individualization of both parties. It treats the other as a half and not a whole. Not to mention the possible consent & communication issues it brings. “I am not whole without you.” You are, and should be. Truly dynamic of all time.