knew who [someone] was
Al comienzo, Tom no sabía quién era Mary.
At first, Tom didn't know who Mary was.
Tom ni siquiera sabía quién era María.
Tom didn't even know who Maria was.
He knew who I was.
Ella dijo que sabía quién era el verdadero líder de la Red Antillana.
She said she knew who the real leader of the Antillean Network was.
— La diva (1981)
Nobody knew who he was.
Tom probablemente sabía quién era yo.
Tom probably knew who I was.
I knew who he was.