Which is the base language for Kotlin?
There is no 1 base language for Kotlin. The designers looked at other languages to see what worked and what didn’t, and combined the good features into 1 language while trying to be consistent, clear, safe, etc.
But in general Kotlin looks like it is from the C family because of the curly braces.
According to Wikipedia, Kotlin is based on Java, Scala, Groovy, C#, Gosu, JavaScript and Swift.