I’m sorry to tell you that if your father left a will leaving everything to your stepmother and your stepmother then leaves a will leaving everything to her children and leaving you and your siblings out, there is nothing that can be done about that.
You need to know what’s in your father’s will. Ask your stepmother and if she either doesn’t have a copy or doesn’t know or is reluctant, you can get a copy from the Probate registry for £10.
depending on the terms of your late father’s will, you may be able to do something or you may not.
You would all have a claim for part of your stepmother’s estate if she promised that you would be looked after and you all relied on that promise to your detriment. For example, she promises to leave you something if you look after her. It needs to be something which is to your detriment. Then, can bring a claim in Promissory Estoppel. It’s a complicated area of law and not an easy or cheap or risk-free claim to bring.
Can I clarify anything else for you?
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We can still exchange emails. Best wishes. FES.