I hate walking into these things late, as I'm not motivated to read all the other threads and there is amost assuredly some information there which would change my answer. However, let me see if I understand this.
1. Mom with a lot of stuff dies.
2. She had so much stuff that taxes would be due on the transfer.
3. Heirs don't like to pay taxes so make a private arraingement to divide some stuff outside of the overview of the court.
4. Stuff is at location where brother (and heir) lives.
5. Other heirs come to get the stuff, but brother won't let them have it.
Is that right?
First, while the facts are not entirely clear, it appears to me that tax fraud is being attempted. Felony go-to-prison or at least huge penalties--tax fraud. Second, since the property has not passed through probate, the estate still owns it. Not the heirs, the estate. While the estate may have some claim against the brother/heir for conversion of the property, the heirs do not. It's not theirs until the court says it is. I enthusiastically await the argument in court, "Your honor, my brother will not allow us the fruits of our felony. Please force him to do so."