You will need to file 2 separate probate actions: one in the United States and one in China. In the United States action, you will need to ask for a declaratory judgment interpreting the ambiguity of the will.
You also to file for probate in China because that is were assets are located.
The problem I see is that nothing you do in the US may be binding in China, where most of the assets are. I think you need to follow the money and have someone in China assist you.
You might try to have the attorney sign an Affidavit as to what the intent was, when the Will was drafted. That way, if something ever happened to the attorney, that testimony would be preserved. It might have an impact in China, as well.
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I am slightly confused about how many wills exist since you are stating that there is English version or Chinese version. The last will, presumably, the Chinese version would be controlling will. I need to know if Grandmother was living in NJ for sometime prior to going back to China. If she was not a resident of New Jersey, I believe that your only course of action would be to file a probate action in China. Did the son in China probate the Chinese-verison of the will? I am not familiar with Chinese probate law and their notice requirements that may or may not be required son notice potential beneficaries (since the will does mention the three sisters I presume.) I think filing a New Jersey probate action will not be successful.