Asked by cynicalclassicist

What do you think of these claims that Robert could have set Cersei aside? It's a claim pushed by people who refuse to believe Renly knew about the incest and say he wanted Robert to set Cersei aside for Marg. Cersei claims she fears him setting her aside and an argument brought up is that a Hightower King did so thousands of years ago and that Daemon tried to do so. Personally I doubt it would be that easy in a marriage with children but what are your thoughts?

I think it is absolutely ludicrous to claim that Renly had no knowledge of the incest. For one, in order to get the Tyrells on board with the idea that Margaery would be Robert’s mistress-turned-queen, Renly would have needed some guarantee that Margaery’s sons by Robert would absolutely inherit the Iron Throne. That means that not only would Cersei have to be put aside, but the three Baratheon-Lannister children would have to have no rights whatsoever to the Iron Throne, so that none of them could not be used later as convenient figureheads by a pro-Lannister faction. If Cersei were found guilty of adultery and incest, there could be no possible way that either she or the children would be left alive: she would be a queen that had committed treason, while her children would be not simply bastards but “abominations”, and “few would have condemned” Robert for executing them.

Two, and relatedly, the incest was not a well-kept secret at court. Both Varys and Littlefinger knew. Pycelle admits that he knew. Stannis had figured it out, and it was not too long after he brought Jon Arryn on that the latter determined it for himself as well. Tyrion seems to have suspected it by the beginning of AGOT, and maybe some years earlier than that. Is it so impossible to believe that Renly - someone who was at court full-time as the master of laws, who would have had a front-row seat to all the time Jaime and Cersei spent together and away from Robert, who was fostering Robert’s only formally acknowledged bastard who looked extremely like Robert at his own castle - would have picked up on these same suspicions?