is it any right of a brother upon a brother's job which was of his father job

Dear queriest, is it a real query? How can one expect 1/2 share job?  A person who was appointed in a post on Compassionate grounds, that person shall looks after his other family members such as mother, brothers (till the attaining of majority), sisters (upto their marriage) but no half share job.

Incomplete facts of the query.

To provide the job or not depends on the financial position of the family after the death of bread earner and it is a compassionate appointment and not a right.  The choice is given to the family and the family members and mostly the widow of the employer's opinion is considered.  Always think of securing a job on your merits alone and do not expect back door methods or charity.  Focus on your education to secure a better job and never spoil your family relations.  Employers always prefer elderly brother, as the younger brother has many years to study and get a job.

You have not stated the complete facts.