First of all , it is better to know, on whose name the nomination is given by your brother. ( mother or wife)?/
In general, most of them change their nomination to his wife and family members, once married. So what has happened here is not known.
Gratuity is payable to dependents , as per nomination.
I am afraid, i cannot comment on the pension part
24th May 2018 From India, Visakhapatnam