Language test only for citizenship application. (and if they are under certain age at that time)
PGP sponsorship is different from skill immigration like CEC.
They need to be your parents (birth certificate), married/common law (marriage certificate if applicable) and typical IDs.
Their education level, language and other skill are not important. But those information need to be provided in application forms truthfully.
They do need to pass medical exam, police check and background check.
Just follow the application guide.