It depends. If you want the mushy IRS guidance, 

==There is a special exception for “certain incremental costs of investment advice beyond the amount that would normally be charged to individual investor.” An incremental cost is defined as “a special, additional charge that is added solely because the investment advice is rendered to a trust or estate rather than to an individual or attributable to an unusual investment objective or the need for a specialized balancing of the interests of various parties (beyond the usual balancing of the varying interests of current beneficiaries and remaindermen) such that a reasonable comparison with individual investors would be improper.”==

https://www.jdsupra.com/legalnews/certain-expenses-of-a-trust-are-still-51831/

The problem is that they are looking at this only from the perspective of a mythical "individual investor" and not that of an incapacitated or minor beneficiary of a trust or estate.  If the fiduciary was chosen based on skills other than investment management, the fees should be deductible, and eventually a court may agree.