Deceased's Return filing

My Uncle's (senior citizen) treatment was funded by selling his shares -LTCG (nominee mom) and breaking fixed deposits (joint holder uncle and mom) in Feb 2017 exceeding taxable limits. Uncle died in March 2017. None of them filed returns as gains below taxable limits. At this point who should file return - Late Uncle (section 159) or my mom ( inheritance income) for AY 2017-18.