Thank you, ***** ***** helpful. What is not clear is whether he refused/ disclaimed his inheritance in the first place (for whatever reason) - or simply asked you to safeguard his portion.
If the former, he has no control over the monies as they would have reverted back to the estate and therefore passed on to you as the sole remaining beneficiary. Under this version of events, he could actually owe you money.
If the latter, there would need to be a clear agreement about what you were effectively holding 'on trust' for him.
As long as you have an agreement between you as to any monies owed to your brother, and can account for transactions in the event of a challenge, you are not necessarily responsible for any wrongdoing. If you did have an agreement to safeguard his share and borrowed from this without his permission, then this could be more tricky for you.
At any stage, if your brother decides to 'cash' in the loan, he may chose to pursue you through the civil courts for any balance owed to him.
So really this boils down to his willingness to cooperate.
I trust that this assists?
The responsibility to declare your brother's inheritance/ income is also not your responsibility. This does not need to be part of any agreement in my view.
Can I clarify anything further for you?