Inheritance of Property

Hi sir, In a family of 6.. Father Mother 2 Sons 2 Daughters.. Father didn't written any will and he died in last year. With the name of mother one property is written.@2nd son went to the register office with mother and make her to sign with his name. Now remaining kids wont do anything for this??.As @1st Son have no rights now??? [now @ 2nd son in another place and @1st son and mother are in one place].Requesting you to kindly let me know the possible solution in which @1st son will get the share in that property.[As Registration process from govt side going to end... ] There is any possibility if mother can give support now please consider this (because she is in @1st son house) . Before father died..@2nd son and father maintained one joint account as father died so @2nd son took entire money in that.. is there any possibility of the share for this??[Father and mother were with @1st son from past 25 years and @2nd son don't take care of parents but mother loves @2nd son and will do whatever he asks ] Thanks and Regards, Hopeless man