Killing some processes also kills others that I do not want to kill

I am goofing around in Metasploitable and trying some commands. Whenever I kill a process using fuser -k 23/tcp to close the port, I get other processes also killed by the process and their ports closed such as vsFTPD process on port 21. Are they linked and is there a way to kill the one without killing the other? Also, there are processes that are being automatically started once I kill them such as the processes that run on ports 3306 mysql or 8180 unknown. Any ideas are highly appreciated.