Death of Partner with only 2 partner

Nilesh chawla (student) (77 Points)

07 January 2021  

A is the husband, B is the mother and C & D are sons of the A & B, E is the married daughter of A & B.
the partnership was entered between B and C. Now B has expired. 
The partnership contains a clause that after the death of any of the partners, the partnership will continue by adding one more partner from legal heirs by taking the consent from all the existing partners and all legal heirs.

There is no will written by B.
Q1) In this case who will be the legal heirs? 
Q2) What will be the income tax implications?

Q3) What procedures they have to perform when one more family member is admitted as a partner, in income tax & GST?

Q4) What procedures they have to perform if they don't want to add any partner and convert partnership into Sole proprietor in income tax and GST?

Q5) How to cancel PAN number?