Your instincts do you credit: much of this scenario does not fit together.
Now, as a matter of full disclosure, be aware that I am licensed to practice in California and not Wisconsin; the nature of this forum precludes giving specific legal advice on specific circumstances. However, I can speak generally with respect to legal principles involved.
First, you state a scenario where the property was "held in trust."
But some clarification is needed:
Legally, a trust is a relationship with respect to property: Property "held in trust" is actually deeded in the name of the named trusteee, who has a fiduciary duty to managed the property for the benefit of named beneficiaries.
So, describing ownership proportions of property specific "held in trust" does not make sense, and isn't possible.
So the first step is to understand exactly who owned the property and in what form.
This can be determined by reviewing a copy of the deed on file whereever your local property records are kept -- city hall or county hall of records, etc. Be sure to also check the tax records on the property -- who is listed to pay and past due charges.
Once the exact nature of ownership is determined, anyone who thinks they may have had an ownership interest can then determine what their current interest is, and take action to secure it.
From your scenario, it sounds like the property was held either as a tenancy in common or joint tenancy.
It will depend on the exact wording of the deed: the basic difference is who receives the interest in the property on death of one of the co-owners.
In the scenario you describe, because property interests were being transferred by inheritance, I deduce the property was owned as a tenancy in common. And further, I deduce that the owners of the minority proportions, such as yourself and your late brother, merely by consensus allowed your uncle to manage the property.
Tenants in common, regardless of the proportion of their ownership interest, enjoy full right to the entire property. Though it is often true, as described, fractional owners allow the largest proportion-holder to manage it or use it. But the minority proportion-holders are still entitled to their share of the rent or sale, etc.
Unfortunately, they are also responsible for their proportional share of the taxes -- even past due back taxes.
So I am sorry to say, any past due tax bill on that property delievered to proportional owner may well be valid if they indeed possessed a proportion of ownership all these years.
The "lease" you mentioned also does not seem to fit into this scenario.
Also, as a general rule, one tenant in common cannot sell the property without consent of the other tenants in common.
So determining actual ownership of the property, in what form and in what proportions is vital.
Your visit to the property records will also reveal if the lawyer and uncle have "sold" the property, in which case an action for recovery will be available.
At that stage, it is best to engage or at least consult with a local attorney on potention action protect yourself from the credit damage to you that may flow from the unpaid back tax bill, and also to recover the value not only of your share in the property, but your share of rental value all fractional owners are entitled to.