The survey will locate the legal boundaries of your parcel. They may or may not conform to evidence of the boundaries existing on the ground. It is possible that third parties have acquired rights in the property by use and occupation. It is also possible that you brother and the trust have acquired rights in other property through the same process. An Owner's Policy of Title Insurance will only insure interests and except coverage of liens or encumbrances of record. You may want to order a policy or endorsements that provide coverage for off-record items that are revealed through a physical inspection of the property.
This answer does not constitue legal advice, nor does it creat an attorney/client relationship. If you are seeking legal advice upon which you intend to rely, you should hire competent cousel familiar with this area of the law in your locale.
A survey will only disclose the "boundaries" of your property, i.e. where your property begins and ends at your neighbor's boundaries. Title insurance will disclose recorded liens and interests, be sure to aks them to plot easements and to walk them with you once they issue their policy to you. What alarms me is two of your statements. First, you state that your brother has been managing the entire property for 10 years and that "his cooperation is questionable". He may then try to claim that he has equitable title to more than his share. It is best to consult a real estate attorney. If you do not agree on your divsions, the matter may end up as a partition lawsuit.
Disclaimer: Ms. Kermani is an attorney licensed to practice in California. This post does not constitute legal advice, should not be relied upon as such, and does not create an attorney client relationship. Since each solution is fact specific, please consult an attorney and provide them with all the facts and documents at issue. Only then can you receive legal advice tailored to your specific situation.