B2 : do we need BC for applicants for vistor visa?

[aleale]

case:
Applicants:Parents and Grandparents
Sponsorer::H1 visa holder(currently staying in US for 1.5 yrs)
Questions:

Do we need to carry Birth certificate and Marriage certificate of the applicants?

What amount should be enough to sponsor 4 people.I have insisted my family to carry their property, bank statements and tax forms?


Quick response is appreciated.

[txh1b]

In general, they are never asked for in many cases though it is on the list of docs suggested by immihelp. It is to verify relationship more than anything else.