Many thanks for the above. There are two principal elements to this from what you say.
The first is your entitlement to your mothers estate. If your mother did not leave a will, then her property would be divided under the Administration of Estates Act which provides if she was not survived by a spouse (your father?) that her estate is equally divided between her real or adopted children (not step children).
On the basis you were entitled to an equal share of her estate under the above rules, then you are entitled to ask the persons that administered her estate for a complete breakdown of her estate in order to calculate your entitlement. If her estate went to probate you can request a copy of the grant of probate for a nominal sum from the probate registry which will give you the declared figures. If your mothers estate was not large enough to require a grant of probate you would need to rely upon the administrators to provide this information.
The difficulty you may have at this point is the length of time that has passed. The Limitation Act provides that you have 12 years to make a claim against your mothers estate so from what you say you are still within time and in a sense the problem is for your sister and brother rather than you because it is they rather than that would hevto produce such evidence if you requested it but there would inevitably be a potential degree of difficulty in them doing so if they have not kept records. You would need to consider retaining a solicitor to formally subpoena them to produce such evidence if they are not willing to provide you with what you ask for. Following a subpoena they can be compelled to appear before a judge at the Probate Registry to produce the evidence you require and if they don't a bench warrant can be issued for them to be brought before the judge to do so.
Your sister and brother will be personally liable as administrators to you for any monies which you should have received but did not. Whether or not you consider it is worth bringing such an action will depend upon your own views but also in particular your knowledge of the size of your mothers estate. Though in principle you can seek to receover legal costs you may incur in pursuing an action, these would be normally limited to the value of your mothers estate (in todays money now). So in practice this is likely to only be worth doing if your mothers estate was large enough to warrant the trouble or if you feel strongly enough that you want to hold your siblings to account and are prepared to potentially spend your own money to do so.
The position regarding your broach is different. As it belonged to you this does not fall as part of your mothers estate and therefore must be returned to you. The issue here may be proving you did lend it to your mother, particularly after so long, and also the fact that you have allowed your sister to keep the broach for so long without formally making a claim for its return. The Limitation Act provides you have a 6 year period from the date of cause of action (this would have been when she took it rom your mothers house) and based on what you say you may therefore be out of time to seek a return of this item. If you accepted that it belonged to your mothers estate then you potentially still have a claim for it as there is a longer 12 period available for claims for inheritances due though you would not necessarily be able to claim that exact item as you are entitled to an equal share rather than a precise item from your mothers estate.
I am sorry that the legal position is rather complicated but I hope the above answer all your questions? If it does, I should be very grateful if you would kindly take a moment to click a rating for my service to you today. Your feedback is important to me. If there is anything else I can help with please reply back to me though