I don't know that "no contact for awhile" is necessary, but you probably don't want the kids in her care at her home while your brother is around and she is allowing him to suck up her emotional time and energy.
With all due respect, Lexie, what I said was...If the grandmother has a problem with not taking her anger out on the children...then a bit of no contact for awhile might be in order.
Other than that, I agree with the rest of your post.