That actually leads to an interesting scenario if Kevan and Tommen are dead. Who even gets the throne at that point? All the major Baratheon's are dead, all of "Robert's" children are dead, and all of his brother's children are dead. I mean, do they start just going to Lannister's at that point? Hold some kind of tournament? The only person left between the Baratheon's and Lannisters would be... Jaime lol.
Gendry.