The alphabet "j" is pronounced differently in the following major European langauges:
German: junge(yunguh) and
How is the sound so varied in these languages?
I would reverse the question. How is it that such varied sounds came to be represented by the same letter? It is the oral language that is the natural language. The written language is added later.
In Spanish, the sound that is represented by the jota used to be represented by the equis. Examples: Mexico, Texas. The change was part of a general revision of spelling.