Help Needed from members out there!

[123India]

My Parents visa got rejected 2 times sponsored by me, once in august last year and once in jan this year. First time they rejected on the fact that both of their kids are in usa. Second time they asked the same question, then they said there son came back and then the lady asked them to show the son's passport-- which they actually don't have bcos my brother is here in us.Now My brother would be visiting them in the coming months(but coming back), so would there be a chance of getting it if we re-apply for visa when he is there. Also my father is still working so this time i want only my mom to apply for visa.
Also would there be any help from senator letter or something. So if you provide whom to conatct etc; please reply..

Thanks in advance.