Thanks for your question.
I note that "I have not agreed" to her proposed change of Will but I'm afraid it's a testator's right to leave their assets to whomsoever they choose.
In the event of your mother passing away and not providing for your then you may be able to make a claim against the estate under the Inheritance (Provision for Family and Dependent) Act 1976. You must make the application within 6 months of the date of the grant of probate in the estate and you will need a solicitor to do it for you.
The Court will consider what is a "reasonable financial provision" for you and will take a number of factors in to account in determining what is fair (eg. size of the estate, other claims, resources and needs of other family members/dependants, income of you and your brother, the responsibilities the deceased had to you), each case turns on it's own facts and there are no hard and fast rules to work out what amount of the estate you will become entitled to without first having all the assets and liabilities of the estate recorded (this will be detailed upon your mother's death by your executors.
If there is just you and your brother and the house is the main asset which she leaves to your brother (or she gives all of her residuary estate to your brother) then I find it very difficult to believe that you would not be made an award. If your brother disputes your claim then it will be what is called a 'contentious probate" matter and you should take independent legal advice from a local probate practitioner about either negotiating a settlement or making an application to Court.
If your mother dies suddenly and you do not know who the executors are it is very important that you take out a "standing search" of the probate calender against your mother's name, this will notify you and send you a copy of the grant if one is take out within 6 months of the date of the search:-
I cannot stress how important the standing search is, if 6 months pass following the grant of the probate then you will be time barred from making a claim against your mother's estate.
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