My theory is that sheik is actually impas little brother.

Hold on! Wait! Don't throw any bricks yet!

I believe that impa, when she turned zelda into a sheikah boy, she based the image off of her little brother sheik.

He could have still been alive at That point and just had to change his appearance

Or he's dead

Idk

It's how my brain compromised sheik's gender

Don't judge