What is all children are in US (Ref: Parents Visa)

[indian21]

Dear All,

I had a query regarding my parents visas. We are 4 siblings and 3 of them are here in US and one has recently got her J1 visa (though she is currently in India and will be in India at the time of my parents visa interview). My second sister who is a GC holder is sponsoring my parents. I have the following questions:
1. In the invitation letter my sister (sponsor) is sending, should she mention that my parents will visit other children or just keep it to her (as in the sample)
2. If asked the purpose of the trip, should my parents mention "visiting all children" or "visiting my sister (sponsor)"
3. If asked about my sister who is in India should they mention that she has got her J1 or just mention what she is doing in India and use that argument as a basis to come back (I guess it will be a lie as she has already got her visa)
4. Finally, do the chances get diminished if all children are in US and if Yes, do you suggest anything that can bolster their chances.

Thanks in advance.
Best Regards

[immihelp]

1. Whatever the truth is.
2. Visiting family.
3. Tell the truth, exactly the way it is.
4. Yes, but nothing much can be done.