What If Robert & Cersei Had A SON? | Game of Thrones

We go through how the events of Game of Thrones would change if Robert Baratheon and Cersei Lannister had a son, a true Baratheon heir. Would they find love or have the same relationship as they did in the series? Would this new son turn out to be just like Joffrey Baratheon? How does Tywin Lannister play the game in Westeros? Does Ned Stark still die? Does this simple change ensure the Lannister rule for all of the series?