Cause Smenkhkare was the older brother and in the book I am reading it says that Smenkhkare Died during his Co-regent but that is not what the Nefertiti show said.

Which makes sense to me cause that would mean Tut was who was thinking he would become pharoah after his older brother which should havebeen pretty far away then he died tut was the next pharoah and he was not totally prepared. But on the Nefertiti show thay did not even mention that Smenkhkare could have been the older brother of Tut?

I am not sure about the age thing either but I now they thought he could have been the much older brother but how much that means I am not sure.