姉 = ane, which means older sister (in general). 妹 = imouto, which means younger sister (in general). 姉妹 = shimai, which means sister[s].
If you mean the name 'Joe' : ジョー /jou~/ (elongated sound for 'o') If you mean just the syllable 'jo' : Hiragana : じょ Katakana : ジョ
You cannot. The Japanese have sounds for sa, shi, su, se and so. Often however if the character for su is at the end of the word the 'u' sound is almost silent. There are two symbols for this sound....
It is written: 赤
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