Hi @DarkWater,
Welcome to Tiller. I’m in my 13th month of using it and am very happy with its functionality.
Perhaps you could split the trust distributions into two transactions, yours and your brother’s (using Extensions>Tiller Money Feeds>Split Transaction). You could use a Category of Trust Fund, Group = Trust or Investments (or whatever you like,) Type = Transfer, and Hide from Reports for your brother’s share so those transactions are hidden from your Budget sheet. I don’t know if that will also hide them from your Balances sheet and exclude them from your net worth because I’m not in that situation; you might have to play around with it a bit or someone else here can answer.
You could utilize Tags and the Tags Report to further differentiate between your and your brother’s trust distributions. This document is useful: Docs: Tags Report for Transaction Tagging
I hope this is helpful. I don’t have the expertise to address your other concerns, but I’m sure that others here will be able to offer suggestions.
Good luck!
Rebecca