Please HELP!!!

I have 2 Grandchildren and I need to know how do I handle unearned income they receive from their deceased Mother.  They each receive  $5,341.00 ($2040.00 state retirement pension and $3,240.00 SSA).  I am getting conflicting advice....yes you have to file a tax form for each, no you don't have to file a form on them or  you can file their unearned income on their Dads tax form.  Please can some advise me how I need to report their income.