Succession certificate for shares and amount in saving bank

Need guidence in following case:

Hindu male (Deceased) died leaving behind his widow, 2 sons (A and B)  and 1 daughter ( c ).

after year or so wife of deceased has also expired. further in same month one of the son ( A ) of the deceased has also died.

surviving legal heirs are:

1. B (Son )

2. C (daughter )

3. for B (son) who has expired :

his widow and his 2 children.

difficulty is wife of deceased B is mentally not fit to come before the court. 

Hence my query is:

1. Can one of the sons of deceased Mr. B can sign for their mother (i.e. mentally unfit wife of Mr. B)?

2. In succession Petition do we have to mention how to devide shares to each legal heir? They have specific requirement that shares of this sector to be transferred in the name of specific heir.

can any one guide?