How do you write big sister in hiragana?

Answer 1

姉 = ane, which means older sister (in general).

妹 = imouto, which means younger sister (in general).

姉妹 = shimai, which means sister[s].

Answer 2

Older brother is "ani" (written 兄), younger brother is "otouto" (written 弟), or gender- and age-nonspecific siblings is "kyoudai" (written 兄弟).

Answer 3

'Hello sister' would be ねえちゃん、こんにちは (neechan, konnichiwa) in Japanese. The pronunciation would be something like "neh-chahn, kon-nee-chee-wah".

Answer 4

こんにちわお姉さん　（Konnichiwa oneesan)