Advice on Visitor Visa

[HelpWanted]

I am a US Citizen now. I have sponsored my parents for a Visitors Visa in the past, which has since then expired and I am planning on sponsoring them again for another visit.

My niece is in US on F1. She'd like her parents to visit her for her graduation. So my questions:

a) Is is ok for a F1 student to file papers to bring her parents? I am assuming the parents will self-sponsor. I have another niece that has settled in India. My sister and brother-in-law have property in India and he is also working in a Govt job.
b) The reason she will be using is about her impending graduation. Will she have to submit any paper work form the University or will it suffice that she mentions it in the invitation letter to her parents?
c) We have to mention the names of 'relatives' in the application form. Both for my parents & sister. The consulate will know that my parents and sis+bil have applied for visitors visa. Is there a risk of them interpreting this as an intent to immigrate and increase chances of a rejection?

If there is a better approach to bring my parents & bil/sis for a visit, do reply.

Thanks

[jnk]

1. Yes. They can self sponsor the trip. Daughter can send invitation letter.
2. a. Photocopies of passport, visa and I-20.
b. Letter of good standing from department.
c. Invitation letter to parents from school.
3. yes. Not really. As long as they prove their ties back to home country. Visa officer evaluate each applicant individually.

Please find visitor visa process and documents list at,

https://www.immihelp.com/usa-visitor-visa-application-process/