They share a genealogy, but as programs are created and maintained in different languages, developers come to wish for different syntaxes that would (1) reduce how much code must be written to accomplish a common logical task, (2) make the code that's written easier to read/understand, (3) reduce concerns about variable types until runtime, and/or (4) overly restrict not just the variable types but also if/when variables can be modified. This list is not exhaustive.

There is a partial programming language family tree here, showing which languages influenced other languages: https://www.researchgate.net/figure/Genealogy-of-Programming-Languages_fig36_260447599

C derivatives are similar in terms of things like imperative control flow, lower-case keywords like if, mostly insignificant whitespace, { }-delimited blocks, etc., but they can be vastly different in terms of features, semantics, idioms, and typical use cases.

It's like how non-programming languages can use the same Latin alphabet but be vastly different in terms of grammar and culture.