Cancellation of Part of Will

What is the law when an act that is illegal, immoral or impossible is set in the will as a condition for one of the beneficiaries gaining his part?

That obligation or condition is cancelled, but this does not necessarily mean the inheritance of that beneficiary is also cancelled.

What is the situation where a part of the will or a condition or obligation is cancelled?

This does not mean that the remainder of the will, or conditions or obligations in it are cancelled,unless the court feels that they are connected with what has been cancelled, or that the testator would not still want them to stand.

Can a testator set a condition in his will that in order to get his inheritance his son must cut off all contact with his brothers?

No! Such a condition for inheriting is immoral and cancelled.

Can an instruction in a mutual will saying that no changes in it can be made without the other side's consent be cancelled – or must the whole will be cancelled?

It is possible just to cancel this instruction, unless the will would not stand up without this instruction.