Start with the honest constraint: the query volume in this vertical is tiny. Nobody wakes up and types "family office accounting" the way they type "plumber near me". Work arrives through estate attorneys, wealth managers, private bankers, and other principals, and the search that matters happens afterwards, when someone who has just heard the firm's name goes looking for evidence that it is real, established, and discreet. A campaign that measures itself on traffic will look like a failure here. A campaign that treats the site as the thing which survives due diligence is doing the job.
The queries that do exist are unusually specific and unusually valuable. Consolidated reporting across entities, partnership tier accounting, trust and estate bookkeeping, bill pay and household payroll, foundation and philanthropic administration, multi-generational cost basis tracking. Each of those is somebody with a real problem and a real budget, and there is very little written about any of them at a level a chief of staff would find useful. The firms that publish something substantive on tiered partnership allocations or on what an outsourced family office engagement actually covers are, in effect, alone on the page.
Then there is the privacy problem, which inverts every normal marketing instinct. There are no logos to show, no client names to drop, no testimonials without a conversation nobody wants to have. Credibility has to be constructed from things the firm can say about itself: the shape of its engagements, the systems it runs, its controls and segregation of duties, its team's backgrounds, how it handles a transition from another provider. Restraint reads as competence to this audience, and an over-produced site full of stock imagery reads as the opposite.