A U.S. Citizen age 21 or older may petition for parents to become Permanent Residents. A Permanent Resident may not petition for parents. It would be a good idea for you to consult with an immigration attorney regarding the case. Best wishes.
I agree with my colleagues only a U.S. Citizen that is above the age of 21 can petition (I-130) for his parents to come to the US (if you're referring to bringing them as legal permanent residents). You should speak to an immigration attorney in your area. If you're referring to them coming as tourists then that's a completely different thing but if it's for a green card then it's the above.