My brother died. Has no spouse and no children. There are SEVEN surviving siblings, but ONE wants all his goods.
When you say that one of your siblings "wants all his goods," what does that mean? "Goods" is a bit of an odd word to use in this context? Also, are either or both of your parents still living?
She manipulated my brother into penning a letter he left in a security deposit box saying "You can have it all, Special Sister"...but he has no will.
Well...there's a possibility that this letter could be construed to be a will.
Like everyone else, you have dozens of legal rights, and it would serve no useful purpose to try and create a list.
Any of you or your siblings can seek to probate your deceased brother's estate. I suggest you consult with a local probate attorney. For reference, can you estimate the gross and/or net value of your brother's estate?
Maybe a few hundred thousand in IRA/Annuity/Life Insurance.
The life insurance policy(ies) should designate beneficiaries. The IRA and/or annuity may also designate beneficiaries. If they do, they aren't part of his estate and wouldn't be subject to any will or the law of intestate succession.
she already took the car, al the cash in the house, the material possessions, etc.
How much cash was in the house? How did she gain access to his home to take the other stuff? How long ago did your brother die?
Let's say, for simplicity, she was named beneficiary for everything (because you can't put SEVEN people on a document (but you intended fairness)...Can we contest these policies?
First of all, you certainly
can "put SEVEN people on a document" (i.e., name seven different people as beneficiaries). Second, anyone
can contest anything. Do you have a valid basis to contest any beneficiary designations? We have no way of knowing. If, in fact, he designated only one of his seven siblings as beneficiary, that fact alone is not a valid basis to contest the designation.
She's coming after me for the $40K or so I owed him
What does this mean? In what way is she "coming after [you]"? If you owe money to your brother's estate, then the person appointed by the court to serve as administrator of the estate would have standing to sue you on behalf of the estate. Has she been appointed by the surrogate's court to serve as administrator? If not, she has no standing to do anything about your debt to the estate.
By the way, if you owe the estate $40k, then you likely don't stand to benefit at all unless the estate has a net value greater than $280k, so it might be in your best interests to let this go and hope none of your siblings is appointed as administrator and sues you.