Oh right I thaught you meant actual languages like japanese, german etc... which is why i said there is only one (english) used for the actual syntax.
Basically the reason there is many is due to different needs.
J# has been discontinued by the way
C# was new for .NET and was basically designed to take full advantage of NET. It is a modern OOP language and has lots of good technical features in relation to VB.NET which is at its heart, an outdated language and not truly suitable for OOP. However, VB.NET still exists because its easy to learn, thousdands of people know it, and there is billions of dollars worth of code written in it. Same reason FORTRAN and COBOL still exist. Really archaic languages but there are many trained programmers and there is billions of dollars worth of mission-critical code writtem in it.
C# and VB.NET can be converted between fairly easialy.