Beneficiary Who Relinquishes His Share

What happens when a beneficiary gives up his share according to the will, but not in favour of the testator's spouse, children or brother/sister?

If this happens and he/she does not nominate another person to receive the share, then the instruction in the will in his/her favour is cancelled.

What happens with a share which a beneficiary relinquishes his share and does not nominate anyone to receive it?

The instruction relating to that beneficiary is cancelled and his/her intended share is divided up amongst the heirs according to law.