even if the executor files amended returns, you may be too late to claim refunds for any year prior to 2019
you should have filed by mail in every year you were rejected. then the IRS would have asked for proof from each of you. assuming you were the one legally entitled to claim the dependents you would have gotten the money and grandpa would have gotten a bill. you may have a claim against your gandpa's estate but for that you'll need to see a lawyer. meanwhile, if you didn't claim the children you need to amend 2019 through 2021 to claim them.
