Would Robb Stark Claim Riverrun and Harrenhal Without the War of the Five Kings?

Imagine a world where the War of the Five Kings never occurred and all the Tullys and Starks were gone. Could Robb Stark claim both the castles of Riverrun and Harrenhal? And how would the Iron Throne and southern kingdoms react?

Splitting the Titles: Lord of Riverrun and Lord Paramount of the Trident

With the idea of Riverrun, there are two distinct titles to consider: Lord of Riverrun and Lord Paramount of the Trident. These titles do not necessarily have to go hand in hand. In my imagination, Robb Stark might assume the title of Lord Paramount of the Trident, while Bran or Rickon, who is presumably Rickon due to Bran wanting to join the Kingsguard or being incapacitated, would become the Lord of Riverrun and take Catelyn's name. This separation could create a more stable governance structure.

The Complicated Case of Harrenhal

Harrenhal presents a trickier situation. While there is no explicit statement that Minisa Whent's line would follow Sheila Whent's, we can infer that the Whents might inherit due to their proximity in the line of succession. Alternatively, for a more fantastical approach, let's consider a scenario where Robb Stark has a daughter with a woman named Elinor Frey, Sheila's only granddaughter named Melantha. Melantha would then be the eventual heir to Harrenhal. If Melantha ultimately does receive Harrenhal, the answer would be affirmative, as Robb's daughter would become the rightful owner.

Succession and Vassalage

The Lord of Harrenhal is a vassal of the Lord Paramount of the Riverlands, currently the Tullys of Riverrun. In the absence of the Tullys, the title would pass to Catelyn Stark and her children. If only males can inherit, and Catelyn herself is passed over, Robb becomes the heir to Riverrun and Harrenhal falls under his vassalage. However, Robb is also the heir to Winterfell, so Riverrun might pass to Bran instead, allowing for potential unification under Robb. However, such a move would likely face strong opposition from the Iron Throne and the other Great Houses.

Alternative Vassals and Political Landscape

If the Iron Throne or the other Great Houses oppose this, a new Lord Paramount would be found, a descendent of one of Hoster Tully's cousins. This decision would likely exacerbate tensions with the Starks but please the other Great Houses. Conversely, if the Starks are made to feel too powerful, the Iron Throne may also resist the Starks ruling both Riverrun and Harrenhal, ensuring a more balanced power structure in Westeros.