也 marks a parallel situation of a relationship between two events or action - hence, it is translated as "also" or "too".
还, however, indicates an element of surprise - which is why it is translated more as "on top of", "in addition to", etc.
Therefore, **(2)** is simply a counting of the siblings one has - whilst **(1)** places emphasis on the large number of siblings one has:
> Not only do I have seven sisters, I also have one brother.
Here is another pair of examples:
> **(3)** 王老师教语法，也叫汉字。
> Wáng lǎoshī jiāo yǔfǎ, yě jiāo Hànzi
> Teacher Wang teaches grammar, and also Chinese characters.
>
> **(4)** 王老师教语法，还叫汉字。
> Wáng lǎoshī jiāo yǔfǎ, hái jiāo Hànzi
> Teacher Wang teaches grammar. On top of that, he also teaches Chinese characters.
Again **(3)** is a more simple and plain way of putting the sentence. **(4)** is a much more emphatic description of the same: Not only does Mr. Wang teach grammar (which is already hard), he also teaches Chinese characters!
Thus we can see 也 has a much more factual tone, as opposed to 还's extra emphasis or indication of surprise.
Here is an example of using both 也 and 还 in the same sentence:
> I'm now going to the new bookshop to borrow books. There there are English books, and French books. In addition, they have Chinese newspapers. Are you going?
> 》**B:** 我也去。我去那儿还地图。
> wǒ yě qù. wǒ qù nàr huán dìtú.
> I'm also going. I'm going there to return a map.
还hái can also function as a temporal adverb, indicating that "the situation is *still* the case". The action or state represented by the verb began in the past, and continues into the present:
1. 我以前有三个妹妹，现在还有三个妹妹。
I used to have three younger sisters, I *still* have three (none died).
2. 我的孩子今年三岁，可是还不会走路。
My child is three this year, but he *still* can't walk.
3. A: 我们走吧。
B: 还早呢。 我还要在跟丁云谈谈。
A: Let's go.
B: It's *still* early. I *still* need to talk to Ding Yun more.
