naruto for example has huge chakra pool without using a tailed beast same is for sasuke madara and hashirama and that's explained when naruto spams clones to no end and sasuke using nature transformation at a young age meaning ashura is able to pull great physical feats while Indra is able to do the same with spiritual feats so to make this short they are both born with higher standards for their families yeah sure itachi was talented BUT he is not super cuz he has average chakra amount and average stamina unlike sasuke who has crazy and near super human stats that explains why those 4 are like broly from DBZ universe born stronger and also get stronger faster from training not to mention the brotherly bound,rivaly and hatred between the bros reincarnations.