It is certainly worth evaluating with a good personal injury attorney. Initial consultations are normally free and will give you some insight into the strength of your case and likelihood of recovery. It sounds as if your cause of action is sound but that is not the only element to a good lawsuit.
You need a good cause of action (you have), damages (again... you have), you must be within the applicable statute of limitations (this may give concerns but many times these can be tolled), and you must have a defendant with sufficient assets to pay the judgment (I have no idea about this defendant's financial status). Once an attorney has evaluated these things they will give you their best opinion on the chances of recovery and the potential expenses of pursuing the litigation. This will enable you and the attorney to determine whether the case is worth pursuing.
Get more than one opinion (visit more than one lawyer) and make sure to take all relevant documentation with you to the appointment. This documentation should include the nature of the abuse allegations, any criminal convictions that resulted from the allegations, and any documented evidence of damages (financial, medical, mental).
You will not likely be able to sue on behalf of your siblings and will need to involve them in the lawsuit if their damages are to be considered.
Please reply if I can help further.
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