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Yes, according to Oregon law, ORS 125.325 http://www.oregonlaws.org/ors/125.325,
you must file a report annually.
However, you do not have to use an attorney to file the report. As long as the report looks substantially like the form listed above in the code, it should be sufficient.
And on the attorney's fees note, they are not required to base their fee off your brother's assets. They can charge whatever they feel is a fair price for their work. But, on the other hand, you are not required to use them, so you can dismiss their services and proceed on your own. It really just depends on your level of comfort in doing so.