MagicCarpet, my situation is different from yours -and I think easier- in that the Will Writer is still alive. In my case, I did the following, in this order:
1. After I learned what the Will said, I thought about it for a couple of years, expressing my hurt indirectly (oops!), and did my very best to process my emotions and thoughts in regards to it.
2. I told everyone involved that this was not okay for me.
3. I sat with the Will Writer and told WW how I saw the situation and how I felt about it. (No drama, just gentle, matter of fact, "When you wrote... I felt [name emotions such as sad]. It's hurtful for me. I also think it impairs the Recipient now and later."
4. When Will Writer said that's my issue/problem to deal with, I agreed wholeheartedly. Because that's correct.
5. I felt much more at peace since I had processed all the initial emotions, then talked with Will Writer directly and peacefully and honestly. I then processed my feelings and thoughts about Will Writer's response and decisions, and decided on what relationship I would have with Will Writer.
6. I decided what relationship I would (or would not) have with Recipient and Recipient's enablers -what relationship felt healthy for me, all things considered.
7. I reorganized my finances to recognize Recipient's material position, Recipient's Enablers material positions, that I may receive nothing and must, in fact, be prepared to continue a financial life unaided by Family.
So, it was three-fold:
i. Communicating peacefully but honestly and directly with each person involved.
ii. Processing my emotions and thoughts. (Hard work! Including counselling at points.)
iii. Reorganizing my finances to reflect this newly-understood reality (financial self-care).
I surely know how emotionally fraught an unequal gifting can be, and how that can -quite naturally- change relationships. The whole thing is sad. But an unequal gifting is a tool for assessing:
*how am I treated by this person and that person?
*how good/acceptable does it feel for me to be treated this way?
*if not good, how can I rearrange my life to feel truly, deeply well and joyful, regardless of other people's decisions?
A shitty arrangement is an opportunity to assess and work though these pieces, so we can subsequently have a great life.
I, too, heartily recommend the books on boundaries and codependency. More than about unconscious enabling of another, they help us dig into our own Stuff and reorganize our internal state and relational positions so that what others do becomes less intense a matter for us.