Jaime is the Valonqar
Remember that flashback scene with a young Cersei and Maggy the Frog? Well she makes a few predictions that night: Cersei will marry the king, check! Cersei will have three children and they will all die young, check! The king will have many children, also check! Another queen will come along to replace her, one that is younger and more beautiful, that one is coming (we think). And finally, Cersei will die with the hands of the Valonqar around her neck. “Valonqar” is high Valyrian for “little brother” (or just younger sibling depending on who on the internets you talk to). Many have speculated that this little brother to be Jaime and that he will ultimately kill Cersei. This theory has been even further supported by a scene where Cersei and Jaime are standing on large map of Westeros with Cersei standing on a region known as ‘the Neck’ and Jaime standing near the region known as ‘the Fingers’. It’s also worth noting that Jaime killed the Mad King in order to save King’s Landing, might he also have to kill the ‘Mad Queen’ in order to save the capital again??