so there is a 2010 Will
and in 2018 that 2010 Will got cancelled. I assume that there was some document made by your father to cancel the 2010 Will
despite the subsequent cancellation, you can still put the 2010 Will to proof by filing a petition for grant of letters of administration with Will annexed
the legal heirs of your father will have to be cited/notified about the above LA petition
since the second wife had married during the subsistence of the 1st marriage, the second wife is not required to be notified
however her children who are the legal heirs of your father have to be notified
they will obviously object to your petition by putting up the 2018 cancellation as a defense
upon that happening the petition will be converted into a testamentary suit and the court will then decide whether or not to grant the LA to you
you will have to discharge the burden of proof that the 2010 Will is a valid Will and was made as per law whereas your objectors will have to prove their case that the 2010 Will was duly and properly cancelled by the testator in 2018
All of the above will require a trial in which both the parties will have to lead their respective evidences and witnesses
so the ball will be in the Court's hands and it will pass a judgment accordingly