Applying for LPR for unmarried son(over 21)

[second stage 14]

This maybe a topic that's often talked about but I have searched for an hour and haven't gotten a good answer.

My parents are LPRs and would like to sponsor my brother(their son) who is over 21 and currently in the US on F-1(as a student).

Is it better to apply now for their son(Under Family2B) or wait until they are U.S Citizens(under Family1)?

According to May VisaBulletin - For India -> Family 2B date is 01JUL, 2002 whereas Family 1st is 08SEP, 2004

Couple more questions:

1. Will the priority date carry-over if they apply now as LPR vs as Citizens?

2. Will they have to show the ability to support(affidavit of support) even though their son can support himself without any financial assistance.

3. Is there a VJ guideline as to the documents required, checklist etc ?

Thanks!

[Boiler 43,434]

Yes, yes and yes.

[second stage 14]

Yes, yes and yes.

Thank you.

The only link I see is to file I-130 form

Link: http://www.visajourney.com/content/childpet

I don't see anywhere it says to file an affidavit of support(such as I-134) ?

[second stage 14]

after much digging, I only found the following:

"You file Form I-130. Your child, son, or daughter may file Form I-485 when a visa becomes available. See the “Visa Bulletin” and “Green Card” links to the right."

Link: http://www.uscis.gov/portal/site/uscis/menuitem.eb1d4c2a3e5b9ac89243c6a7543f6d1a/?vgnextoid=51ea3e4d77d73210VgnVCM100000082ca60aRCRD&vgnextchannel=51ea3e4d77d73210VgnVCM100000082ca60aRCRD

[wizzard1663 0]

I called USCIS and asked this exact question about sending the Petition now (when my wife has only a Green Card), or waiting until she ultimately has Citizenship. They said to apply now because it gets you into the system and processing much sooner. Once the Petitioner's status changes to Citizen, the Priority is automatically updated.