Title

     Family terms are different for one's family and someone's family. One's family is 家族かぞく. Another person's is ご家族. ご is an honorific prefix that attaches to most Sino-Japanese words. 

      The traditional Japanese house structure, 家(いえ), is very different from a nuclear family.  The 家 is responsible for making contracts with Buddhist temples and is comprised of generations of married couples and unmarried children. Ancestors are thought to watch over their descendants. 

      The wife joins her husband's 家 and has no ritual obligations for her nuclear family. In real life one's nuclear family is still important, but death and lineage is dominated by one's 家. Only one child is a successor, and it's usually the oldest male child. Females are rarely chosen because they would be obligated for both families' rituals. Upon death, individuals who don't receive ritual care become 無縁仏むえんぼとけ. These people include singles, childless couples, etc. Family altar is 仏壇ぶつだん and family grave is 墓はか. Ashes of past generations are kept there. 

       Nowadays, some are veering from this. Some have their ashes scattered and others have a grave plot, but these are hard to get.  

     There are many important people in your family tree 家系図かけいず. Not all family terms have separate terms for one's family and someone else's family. When there is a term that has both an 音読み and a 訓読み, the first is usually for referring to them or in written terms. 

Word Notes:

1. 家内() is felt to be condescending because it suggests that women should be in the house.

2. For writing aunt and uncle, 叔 is used when they're younger and 伯 is used when they're older than your parents.

3. 母親() and 父親() shouldn't be used to address one's parents. 母() and 父() are similarly used. 母() and 父() may refer to the mother or father of anything also. 

4. ～貴() attached to 兄() and 姉() adds respect.

5. As you will learn, you will often or usually call family members with the titles originally for someone else's family. Some here include one's mother, father, grandfather, and grandmother. 兄 is often like this and 姉 is even more so replaced by the term originally reserved for someone else's older sister.  

Examples 

1. 私()は兄弟(きょうだい)が3人()います。
    I have three siblings.

2. 母なる大地　(Set Phrase)

     Mother Earth

3. 姉()は母()に似ている。
    My older sister resembles my mom. 

     The main difference between the words for one's family with that of another is that someone's family is addressed with more honorific terms. The list below illustrates these terms with the same rules of age applying for aunt and uncle as before.  

     Despite there being a great divide in family terminology, there are still many terms that are neutral and may be used for both one's own family and someone's family. Below is a list of the most common of these neutral terms. 

     Family members in this group can still be made polite in reference to someone else. For example, the nephew and niece of another person can be referred to as 甥ごさん and 姪ごさん respectively. Other family members are simply discussed, if necessary, with ～さん to be polite. 親御おやご is a similar looking word that may respectfully be used to address someone's parents.

 Ancestor

  先祖 typically refers to one's ancestors, particularly those in your 家. You may hear people refer to them respectfully as ご先祖さま. You never hear ご祖先さま because 祖先 is impersonal. 祖 refers to the founder of a lineage, dynasty, or even a field of study. "Ancestor" as in biological origin is normally 始祖.

After Grandchildren

It's interesting to know that Japanese has words for those who have not just great-grandchildren, but offspring for 8 generations ahead of you (just in case you live that long). The terms up to great-great-grandchildren are usually known by most speakers. The others are just fun to look at. 

     The word for cousin, いとこ, is a very odd word to write in Japanese. It is written differently depending on the age and gender relationship with the speaker. 

Word Note: You may also use the 音読み of the characters to distinguish.

     Many speakers will call their mom, dad, older brother or sister, and grandparents with the terms that are supposed to be for someone's family. But, if you use them for you own, you may slightly change their appearance. For example, instead of -さん you might choose -ちゃん or drop -さん altogether. It’s also even possible to drop the お- at the beginning of these phrases. 

6. お母()さん、おもちゃほしい！
    Mom, I want a toy!

7. お父()さん、ほんとにしゃべりすぎだ。
    Dad, you really talk too much.

8. 姉()さん、何()してる？
    Hey sis', what are you doin'?

     To create the terms for half-brother and half-sister, you first must decide whether they are from a stepfather or a stepmother. For each combination, there is a technical, conversational, and insensitive term available.

The technical terms utilize Sino-Japanese vocabulary. The conversational terms are the native vocabulary equivalents of the Sino-Japanese terms. The insensitive terms utilize the terms 種違い (of different seed) and 腹違 い (of a different womb) to refer to "by a different father" and "by a different mother" respectively.