You are asking a legal question. My suggestion would be to consult an attorney, as we are not attorneys.
From the real estate standpoint I would say that it would depend on how the trust is designed. Most real estate contracts provided by the Calif. Ass'n of Realtors of space for two parties. I went to a seminar where we learned how to have up to six people on a contract.
Technical limitations aside, working in a transaction and everytime a change is made having to obtain four or five approval makes it very cumbersome for all parties. You might want to also ask the attorney the best way to structure the trust to facilitatte what the trust wants to accomplish.
Hope this is helpful