What would it take for me to believe my family could thrive without my control?

Usually a forced experiment. Kris Kluver, in The Dysfunctional Family Office, has Robert Mitchell answer this question by leaving for Cayman with no laptop and no phone for an entire month. The month forces him to discover what he could not have proven to himself in advance. The family can run the company without him. The kids handle the hard decisions. The team holds. The business grows. The forced experiment usually has to be deliberate because most founders won't naturally step away long enough to find out. The belief follows the evidence. Founders who trust their family to thrive without them are usually founders who have already seen it happen. The question isn't whether your family can thrive without your control. It's whether you're willing to find out.