The simple fact that a will and trust are not "favorable" to you and your brother will not be grounds for successfully challenging these documents. You will need to prove that your father:
a) lacked testamentary capacity at the time that he executed these documents; and/or
b) was under undue influence when he signed the documents.
Please retain an experienced probate litigator who can review this situation and determine whether you have any grounds for challenging your father's estate planning documents. Good luck to you.
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You would have to consult with an attorney in Mexico, but with respect to the California property, the court will not be compelled to follow a ruling by the Mexico court. In addition, it is doubtful even if you could get into a Mexico court that they would want to get involved in this matter.
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You need a Mexican lawyer to answer a question like that. But a will of a non-resident decedent can be probated in American courts under certain circumstances which will be stated in state laws, and if it can be probated here then perhaps it can be challenged here as well, depending on the laws of the jurisdiction.
Ownership of Mexican land situate within a certain distance of a coast or border, by foreigners, is limited by the Mexican constitution; but in those regions I am told that it maybe owned by US citizens via a trust format known as the fideicomismo, which involves a bank typically acting as trustee and owner of record for the American's beneficial interest. Whether or not such trusts can have a testamentary element I do not know, but that would probably be something you should ask if you are hiring advice in Mexico.
No legal representation exists by virtue of this answer. Consult your attorney. Licensed to practice law in Indiana and Illinois. Circular 230 Disclosure: any U.S. tax advice contained in this communication is not intended or written to be used, and cannot be used, for the purpose of (i) avoiding penalties under the Internal Revenue Code, or (ii) promoting, marketing or recommending to another party any matters addressed herein.