verys

I don't know if it's confirmed, but theoretically, yeah.

I don't know if this is accurate, been theorised already, or been disproved, but I think the Sibling is Urithiru itself, much as the highstorms are the Stormfather. Since Urithiru is deteriorating because the Sibling is 'slumbering', I assume that, just as the highstorms are the Stormfather's doing, Urithiru is what the Sibling was in charge of. There's a pillar of crystals in the room where Re-Shephir used to be (referred to as the heart, somewhere), and in chapter 109 of OB Navani and Dalinar inspect some 'veins of garnet' found in the strata. Renarin theorised that Urithiru was a huge fabrial (OB, ch. 44), but this hasn't been proved. Probably. Now that I think about it, this theory is probably wrong, but it's just an idea. So, thanks for reading. -verys