macOS is absolutely not a FreeBSD fork, but there are lots of bits and pieces in current macOS that are direct derivatives of FreeBSD code, including kernel code, libc and lots of userland stuff.

https://developer.apple.com/library/archive/documentation/Da...

"The BSD portion of the OS X kernel is derived primarily from FreeBSD, a version of 4.4BSD that offers advanced networking, performance, security, and compatibility features."