Can a NRI operate his mother or sister account The trading account / bank accounts of sister(unmarried) or mother linked with her demat account
It should be alright if you are not doing it for any consideration. By the way, there are no explicit regulations around this.
I had written this sometime back.
why can’t mother hire the son for salary / commission to manage her trading account ?
If you start taking consideration, that will turn this activity into something you do as a profession. And the link I shared earlier has all the legal ways in which you can manage money for others.