Based on the description, if you are in a room that cannot be behind the parent's bedroom, you can only be in your own bedroom (Fabio's bedroom) or in your sister's bedroom (Tatiana's bedroom), as both of these rooms are adjacent to or in front of the parent's bedroom. Since the question specifies "cannot be behind the parent's bedroom," the only possibility is that you are in:
His sister's bedroom (Tatiana's bedroom).