I'm rewatching Nanatsu no Taizai, and many of the members (Meliodas, Ban, King, Gowther, Diane, Escanor) didn’t recognize each other at first, or they weren’t sure about the others really being who they were. Some examples,
Ban after re-meeting King: And you, who you are?
Diane after meeting Meliodas: Are you a holy knight?
Escanor after meeting Ban: haven’t I seen you before?
Gowther after meeting Meliodas and Ban: yes, I really am Gowther. Those traits, that posture, that scar, as I thought, you are undead Ban. That means the young guy whose appearance is similar to Meliodas is..
Meliodas: that's right, I'm Meliodas.
Gowther: what a surprise.
Ban: and what do you think of him. I bet you'll be surprised more he's King.
Gowther: No, he is another person
Why did this happen? Supposedly people like Meliodas and Ban didn’t change their appearances and they only separated 10 years ago.