Visitor visa for sister and neice

[ngracias]

By Brother's family is planning to visit me next year. He and his kids already got a visa. My sister and my neice do not have a visa, nor do they have travel history.
My sister will be travelling with my brother. Her husband and in-laws are not travelling with her. She is a housewife but has good amount of assets and bank balance.
I am a US citizen and work for the government.
I want to know what the best way would be for her and her daughter to apply visitor's visa (through sponsorship or on her own or showing my brother's visa)

Thanks

[peace999]

Self funding is always better especially in people who are working age. But they look at income rather than bank balance. Your sister being a house wife should show her husband is spending for the trip. And they will want to know how much he is earning and proof of that ( salary slip/ tax return).
10-12 L/yr should qualify. If less, you can send papers ( I-134 )

Your brother's visa won't have any effect on her application. But yes, she should take a copy of that to the i nterview since she is showing that she is travelling
with them.