system
Given the following post, respond as if you're commenting on Reddit:
human
[Game of Thrones] [Spoilers for previous seasons] What if...

...Tommen had been the eldest surviving child, rather than Joffrey? 

Suppose that Tommen were just as sweet-natured as he was portrayed, but he had been older than his crap brother Joffrey? Starting from the royal visit to Winterfell, and assuming that all other factors up to that point were the same, how would the story play out differently?
gpt
Ultimately the same. Tommen and Sansa are betrothed, the Starks head south to King's Landing, still without Bran as nothing changes on him getting crippled, and Ned eventually discovers the truth about Tommen's parentage.

Ned is likely still betrayed in his attempted coup after Robert's death, but Tommen spares him and sends him to the Wall.

When Jeor Mormont, the Lord Commander of the Night's Watch, is killed beyond the Wall, Ned Stark becomes the only real candidate to replace him and Jon Snow remains an unpopular regular soldier, possibly even more so now that his dad's in charge.

Meanwhile, back down south, Renly and Stannis have still both claimed the throne and civil war breaks out. It goes the same way it did before, but with one major change: Tommen does not break off his engagement to Sansa and the Starks become tied to the Lannisters through a marriage that might actually work.

Up North, Robb Stark, new Lord of Winterfell, has to decide where he stands in the new chaotic world. He calls his lords to him, seeking a council. Greatjon Umber declares him King in the North anyway and so it begins. Sansa sends a letter asking him to end the uprising, but he disregards it just as he did OTL.

Beyond that, we're getting into write a whole new book territory, so I'll leave it at that.