Older sibling in Japanese

There are two Words for older brother, and they are used in different contexts.

When talking to someone else and you refer to your older brother, you use a humble form. You would say "ani" (hiragana: あに kanji: 兄).

When talking to someone else and you want to refer to their older brother, you use a polite form. You would say "onii-san" (hiragana: おにいさん kanji: お兄さん). You also use this Word when talking to your older brother. So if I had an older brother I would call him "onii-san" or "onii-chan".