A person who flies in space is called an astronaut.
They'd be called that person's relative.
a person who does not exercise is called a layman.
That person may be called a victim. If the person does not survive, the person can be called a casualty.
When a person imitates another person, it is called mimicking or copying.
A person from Iraq is called an Iraqi.
A person is called an "Olympian" when they are in the Olympics.
the person is called a chaufer
The person is called the loser.
A person from Cameroon is called a Cameroonian.
The person is called an archaeologist
A person from Dover is called a Doverite.