Your father is 父 [ちち].  Someone else’s father is お父さん [おとうさん].  Your mother is 母 [はは].  Someone else’s mother is お母さん [おかあさん].  You can, of course, call your own mother and father the more polite version, but it would be bad form to call someone else’s father 父 [ちち].  If you want to up the politeness a bit, you can use the 様 [さま] suffix instead of さん.

Here are some other permutations:

• 父ちゃん [とうちゃん] ・ 母ちゃん [かあちゃん]
• パパ ・ ママ
• 父親 [ちちおや] ・ 母親 [ははおや]

If, for some reason, you should find yourself in pre-Meiji Japan, you might want to use 父上 [ちちうえ] and 母上 [ははうえ] to fit in.  I believe this can also be used when writing very formally in reference to someone else’s parent.  One of my favorite research websites, SpaceALC presents the following example:

母上がお亡くなりになったとのこと。お悔やみ申し上げます。 Please accept my sincere condolences on the loss of your mother.

In English, we just refer to our siblings as “brother” and “sister.”  However, there is a plethora of ways to address different members of the family in Japanese.

Sisters

姉 [シ・あね] – Elder sister

妹 [マイ・いもうと] – Younger sister

Depending on your relationship, you might call her おねえさん (“elder sister”) or just おねえちゃん (“big sis”).  You can also just use あね.  You can even leave off the お prefix if you’re talking about your sister, and call her ねえちゃん or any number of permutations like ねえちゃま, which is sort of a cutesy mishmash of ちゃん and 様 [さま].

Generally, if you’re using the more polite さん suffix, you’re probably talking about someone else’s sister.  I’ve even heard the term 姉上 [あねうえ] used for an elder sister, but it sounds very formal to me.

If you’re talking about multiple sisters, you would use the word 姉妹 [しまい], or “sisters.”  Do you notice how it’s just a combination of あね and いもうと?  Do you also notice how the pronunciation is derived?  Why is the word しまい instead of あねいもうと?

Confused yet?

Brothers

兄 [キョウ・あに] – Elder brother

弟 [ダイ・おとうと] – Younger brother

The same holds true for talking about brothers as it did for talking about sisters.  You can call your own older brother あに, but when you get into -さん and -ちゃん suffixes, things change slightly:  おにいさん ・ おにいちゃん.  The more formal 兄上 [あにうえ] would again be a way to refer to someone’s brother.  If you listen to the Japanese dialog in “The Last Samurai,” you might hear this usage when Katsumoto (Ken Watanabe) is addressed by his sister Taka (Koyuki).

If you have brothers, you have 兄弟 [きょうだい]. This is also how you would refer to “sisters and brothers” or “siblings.”

Are you starting to see any patterns?