You are in:

A country that permits polygyny (a man with two legal wives).

Your sister and you share the same father but different mothers.
Each of the mothers gave birth on successive days.
Your sister is still your sibling, which explains your love for her.

Granted, she would be your step-sister, as you share only one parent.

You are in:

A country that permits polygyny (a man with two legal wives).

Your sister and you share the same father but different mothers.
Each of the mothers gave birth on successive days.
Your sister is still your sibling, which explains your love for her.

Granted, she would be your half-sister, as you share only one parent.

You are in:

A country that permits polygyny (a man with two legal wives).

Your sister and you share the same father but different mothers.
Each of the mothers gave birth on successive days.
Your sister is still your sibling, which explains your love for her.

You are in:

A country that permits polygyny (a man with two legal wives).

Your sister and you share the same father but different mothers.
Each of the mothers gave birth on successive days.
Your sister is still your sibling, which explains your love for her.

Granted, she would be your step-sister, as you share only one parent.