Yahiko and Nagato barely fit the Naruto/Sasuke relationship if they even register to fit it at all. There was never any real hostility or rivalry between them and they always seem to look out for and respect each other and Nagato's dream quickly became the same as Yahiko's. The others you mentioned do have the Naruto/Sasuke relationship but Nagato and Yahiko really don't have many traits of them. It's why I like them so much.
Originally Posted by Ver-mont
Parena or Serecham both equal Serena+Pancham! Sereevee or Serevee equals Serena+Eevee!