second time parents visit - but the sponsor is different

[iamarun]

hi,

My parents have a 10 year multiple entry b2 visa. And they visited me once 7 years back. (to california)

Now my mother is planning to visit my brother's family (near boston) using the same visa. She will be travelling with my brother's wife.

I am thinking of making my mother carrying a letter from my brother as sponsor for the trip/stay. Will this be OK? Do we need to fill I-134 form or provide employment/bank-account details of my brother.

Please help

thanks..

[note: i tried searching using keyword second/second visit/2nd visit and could not get any results :(]

[immihelp]

Just letter is fine.