Do you even allow accounts where the trustee is a corporation?
The law of your state should describe who can serve as a trustee, but I sincerely doubt that a garden variety corporation can be the trustee on a family trust. Even banks must have trust powers to serve in that role.
Your customer or your customer's lawyer has cooked something up that I would not care to taste. Talk to your own counsel to see if you can accept this one. If you can accept it, talk to yourself about whether or not you want to.