Inspired by several recent questions about siblings.
My little sister was born a day¹ after me. Yet, we are not twins. I love her very much.
Now the question:
Where am I?
EDIT: yes, the intended answer is about (realistic) people in our real world.
Hint 1:
She's a woman, I'm a man... but there is no incest.
Hint 2:
Tags are important.
EDIT2: some answers, especially this and this are close and in the spirit of the intended answer (but they are slightly circumventing the question). Thus it's just a matter of knowing/guessing:
the specific language that fits the question
and I'll reveal the answer in some days if not guessed by then.
¹ Not really important that this is one day - could be a few days, a few weeks or whatever...