1. The usual convention, albeit is not a legal rule, is that there would be a reading of the will of your deceased mother about one week after the funeral at which all interested people would attend and hear the terms of the will. In the situation where there is a will but you as son has not been told its terms, you should formally write to your sibling who has a copy of the will and request a reading of the will or a copy and the name(s) of the executor(s), in default of which, make clear that you will issue a citation to whoever is named as executor to administer the will or else renounce their rights to do so. Be aware that your sibling sister has no right to take control of your dead mother's finances without being named as sole executrix under the will. So be aware from the outset that if this is happening, it is probably outside the law. Be aware additionally, as you have a right of action under section 117 of the Succession Act, 1965, to make a potential claim if your mother failed her moral duty to make proper provision for you under the terms of the will, you have a right to be told by the executor whether you are named in the will or not. Here the six month time limit to make a claim under this section runs from the date of the grant of probate.So you should be clear of your rights.
2. Be aware that at law, it is the residuary legatee who is the only person who has a right to a copy of the will prior to it being lodged for probate. Once the will is lodged for probate, then it becomes a public document and any member of the public, including you, can inspect and take a copy of it at the Probate Office in Dublin 2 beside the Four Courts.