Oniichan, Oneechan, Otouto, Imouto

Brothers and sisters, we are here united on this day to talk about the difference between "brother" and... "brother"... in Japanese. And "sister" and "sister." Of course I'm talking about the words oniichan 御兄ちゃん and otouto 弟, and oneechan お姉ちゃん and imouto 妹, and some other words related to siblings.

Otouto 弟 vs. Oniisan お兄さん

The words otouto 弟 and oniisan お兄さん both refer to someone's "brother." The difference between otouto and oniisan is that otouto always refers to a "younger brother" or a "little brother," while oniisan refers to the "older brother."

Imouto 妹 vs. Oneesan お姉さん

Likewise, the words imouto 妹 and oneesan お姉さん refer to someone's "sister," and the difference between the two is also that imouto refers to a "younger sister" or a "little sister" while oneesan refers to an "older sister."

What Is Not An Imouto or Otouto

Since this is actually easy to mistake, let me make it very, very clear.

Younger Sibling not Youngest Sibling

These terms are all relative. That is, otouto and imouto are younger while oniisan and oneesan are older siblings. This means they are younger and older than someone.

It does not necessarily mean that otouto is the single youngest brother someone has, and oneesan isn't necessarily the oldest sister someone has.

For example, a single oniisan can have 2 otouto's. The youngest girl of 3 daughters would have 2 oneesan's.

"Little" Brothers and Sisters

In some cases imouto and otouto are translated as "little sister" and "little brother," but that's just how English says it. You can have an imouto or otouto that's 2 meter tall and taller, bigger than you. So long as they are younger than you they are still imouto or otouto. It's not the size that counts.

Oniichan, Oniisan, Oniisama, Oneechan, Oneesan, Oneesama

You might have noticed that some characters call their older brothers oniichan, others call them oniisan, and others oniisama. But wait a second, what's the difference between oniichan, oniisan and oniisama?

As you probably guessed, this is actually related to the Japanese honorifics kun 君, chan ちゃん, san さん and sama 様, except there is no oniikun. When someone says oniichan, the chan there implies intimacy. And when they say oniisama, the sama there implies the utmost respect. By the way, oniisan is neutral and implies nothing.

The same is true for oneechan, oneesan and oneesama.

As if that wasn't enough the o is actually a prefix and is optional. Actually, even the san is optional. That means all of the following words mean "older brother" in Japanese:

nii 兄
niisan 兄さん, niichan 兄ちゃん, niisama 兄様
onii お兄
oniisan お兄さん, oniichan お兄ちゃん, oniisama お兄様

And for "older sister":

nee 姉
neesan 姉さん, neechan 姉ちゃん, neesama 姉様
onee お姉
oneesan お姉さん, oneechan お姉ちゃん, oneesama お姉様

Other Words for Brother and Sister

Besides the words above, you can say older brother and older sister in Japanese the following ways:

ani 兄 and ane 姉
aniue 兄上 and aneue 姉上
aniki 兄貴 and aneki 姉貴
Brother and Sister

The words aniue and aneue have a more polite, respectful tone to them.

Meanwhile, aniki and aneki are also a way to call the "boss" of your gang. Normally the boss is a guy, so aniki, but if the boss is a girl, then aneki.

Kyoudai, Shimai - Brothers and Sisters

Behold the Japanese language! When you have two brothers, one must be the ani 兄, the other, the otouto 弟, together, they combine, to form... *drum roll* ...kyoudai 兄弟!!!

No, really. I'm serious.

The word for "brothers," two or more, in plural, is kyoudai and is written with the kanji for older brother and younger brother together. That's because a single kanji can have multiple readings.

The brothers, or kyoudai 兄弟, Kamina and Simon, ani 兄 and otouto 弟 respectively, from the anime Tengen Toppa Gurren Lagann 天元突破グレンラガン

As if that wasn't enough, you can actually join ane 姉 and imouto 妹 to form shimai 姉妹, which would be the word for "sisters."

The sisters, or shimai 姉妹, Ram and Rem, ane 姉 and imouto 妹 respectively, from the anime Re:Zero kara Hajimeru Isekai Seikatsu Re:ゼロから始める異世界生活

But wait! There is more! Since there's a 50% chance the pair of siblings aren't the same gender, often, in manga and written Japanese, you get stuff like kyoudai 姉弟 or kyoudai 兄妹. It reads the same as the kyoudai 兄弟 from before, but the kanji written change to match the genders of the siblings.

(technically, the words should be read as keimai 兄妹 and shitei 姉弟, but nobody reads them like that)

You can also combine all four kanji to make the word kyoudai shimai 兄弟姉妹, which is how you say "brothers and sisters" in Japanese.

Different Romaji

The words kyoudai, oniisan, oneesan, imouto, and otouto are sometimes spelled differently.

kyoudai vs. kyōdai
oniisan vs. onīsan
oniichan, vs. onīchan
oniisama vs. onīsama
oneesan vs. onēsan
oneesama vs. onēsama
oneechan vs. onēchan
imouto vs. imōto
otouto vs. otōto

This is just the same word written with different romaji. Neither of the above is wrong. It's just that one uses a macron for long vowels while the other does not.

Referring to Other People's Siblings

Although most of the time oniisan, oneesan, imouto and otouto are used to refer to your own siblings, these words can also be used to refer to other people's siblings too. For example:

anata no oniisan あなたのお兄さん
anata no ani あなたの兄
Your older brother.
anata no otouto あなたの弟
Your younger brother.
anata no oneesan あなたのお姉さん
anata no ane あなたの姉
Your older sister.
anata no imouto あなたの妹
Your younger sister.

In the cases above, the word is based on the age of the siblings, not your age. That is, if you are 500 years old, somebody else's oneesan doesn't become an imouto to you just because you're older. If A calls B their oneesan, then you must call A's sister their ane, not their imouto.

Age Unknown

If you don't know the age of the siblings the words kyoudai and shimai work too. Even in the singular, since plurals in Japanese are a bit different.

anata no kyoudai あなたの兄妹
Your brother. (male)
Your brothers. (male)
Your sibling. (neutral)
Your siblings. (neutral)
anata no shimai あなたの姉妹
Your sister. (female)
Your sisters. (female)