Can our estranged, eldest sister contest our affidavits, even though the entire family has given written consent confirming our brothers last wishes?

I'm not sure these affidavits will work, but a judge may accept them. Typically your options are to accept the property or disclaim it. If you accept the property you can then give it to your youngest sister. In accepting it, you don?t have to physically take it, but you can have your share given to your sister. I think that?s how the affidavit would have to work. In that case, your kids would not be a part of this unless they were claiming you were not competent to make decision and affidavit. Alternatively, if you were deemed to disclaim the property, it would be treated as if you predeceased before your brother. In this case, you would have a problem because your disclaimed property would go to your kids. Therefore, you will have to do something that acts as you accepting and gifting the property to your youngest sister.

If your brother did not leave a will, then his "last wishes" will have no legal force or effect. His estate will pass to his legal heirs. Those that don't want their share can certainly gift it back to another sibling. I strongly suggest that someone retain counsel to sort through all of the issues.

Your affidavits are meaningless. You each can disclaim your interest in the estate, which would result in the eldest getting more, but the eldest does not have to agree to it. She is entitled to her sixth.

Your brother did not make a will. No other direction from him has any legal effect on his assets subject to probate. The siblings that want to honor his declared wishes would be making a gift of their share of the brother's estate to the younger sister. If a sibling does not want to make a gift he or she does not have to. If there is no will the brother's estate must be opened in probate so an appointed representative has the legal authority to distribute his assets in accordance with the statutory rules of descent and distribution.