They can have a similar pronounciation when the "i" modifies some other vowel. An "i" on its own (vowel) is different from a "j" on its own (consonant), though the mouth position is not so different (but there is a difference). In Chinese, you don't notice the similarity because of the consonant-vowel-consonant syllables. Kind: "i" ist: "i" Jäger: "j" Dia: "i-a" Maier: "j" Leier: "j"