Just remember that there are no "trust police". You can put rules or requirements in a trust document....just like an executor can (literally) do almost anything with the funds in your estate. It's up to someone else to challenge the executor and bring a legal action against them if they aren't doing what they are supposed to do. So don't assume that just because you put whatever in your trust that it has some magical powers to make it so - so make sure you have full confidence in your choice of executor, because it would take someone with a strong backbone to challenge them and enforce justice if they aren't doing what they are supposed to be doing...
DH's uncle was the trustee for the grandparent's trust. The uncle and DH's mother were the only children. The trust was written for half of the assets to pass to the grandchildren if DH's mother predeceased the grandparents.
DH's mother died from complications of Parkinson's several years before the last grandparent died. The uncle proceeded to have the last grandparent sign away assets to him. When the last grandparent finally died at the age of 96, the uncle refused to provide an accounting of the assets of the estate. There was a beachfront apartment and a house in the Midwest, along with quite a bit of blue chip stocks, amount unknown.
Remember, the uncle was the trustee of the estate.
DH's siblings (total of four grandchildren) were initially reluctant to engage in a legal battle with the uncle, but were forced to eventually hire an attorney. The first attorney was incompetent, but by the time that was determined, a year had already passed. The next attorney recommended arbitration, since it was apparently impossible to prove that the grandparent was not aware of what documents had been signed giving the uncle ownership of property.
The siblings were completely bamboozled by their uncle, who would only agree to pay each of them a set amount, without revealing the size of the estate. And, like Moorebonds said, there has to be someone willing to challenge the trustee. In their case, no one had the stomach to challenge what was occurring, and were heartbroken that it was a blood relative who cheated them out of at least a clear accounting of the assets.