My wife of 30yrs refuse to part her super to me, page-14

My wife understands that bequeathing money away to her siblings means that HER children will not benefit.
Your wife's sister's children will benefit...look at a family tree and you will see how families separate ...
Your children's children and their children will not associate themselves with your wife's siblings future families .

I think you could/should actually talk to your wife and tell her that HER future generations will not benefit from her charity to her sister.