Question Summary:
It is permissible for an heir to waive his/her rightful share from the deceased’s estate in favour of another heir

Question Detail:

Can a muslim waive his right to inherit from the deceased in favour of another heir? Is such a waiver valid? 

Answer :

In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh
It is permissible for an heir to waive his/her rightful share from the deceased’s estate in favour of another heir.
 
And Allah Ta’āla Knows Best
 
Mufti Ismail Desai,
Darul Iftaa
 
Checked and Approved,
Mufti Ebrahim Desai.