Your International Program  Center will send an invitation letter to yr parents asking to join for the commencement if you provide them with the address. You will also need yr official transcript and your personal letter to the counslate requesting to grant them a visa in order to attend yr commencement . Make sure in your letter that they dont inted to stay and will go back.. u wil make sure they will abide by the laws of us while they r here.

when they r having interview  ask them to show ties  and responsibilities like work , properties to take care of  and siblings ... which shows they have to and will return.. if all yr siblings r abroad tell them not to mention that.. coz they wont have any reason to go back.. that is what the consulate thinks..

apart from  this they will need other financial documents  to show that they have  enough to support themselves while in US ..would not have to depend on u..

this is as far as i know..

All the best!!!!