AU where Shadow has always been known as "Shadow Robotnik" (since Dr. Gerald calls him "my son" in Shadow 2005), and when he has amnesia, he has no idea at first that Ivo is descended from Gerald because he always calls himself "Doctor Eggman".
Eggman: You must obey me! You were created by my grandfather, Dr. Gerald Robotnik! You --
Shadow: What!? You're my nephew!?
Eggman: (confused angry noises)