Why shouldn't the sibling running the company get bigger distributions than the others?

Because tying distributions to effort creates a permanent underclass inside your own family. Kris Kluver, in The Dysfunctional Family Office, makes this point directly. The salary already rewards the work. Distributions reward the ownership. If you tie the distributions to effort too, you're paying the working sibling twice and the non-working sibling not at all. The sibling not in the business starts feeling like a second-class family member. Resentment builds. They eventually demand a buyout or become a hostile minority owner. Either way the family fractures. The right answer is harder for the working sibling to swallow upfront and much better for the family long-term. The market-rate salary covers the eighty-hour weeks and the EBITDA growth. The equal distributions hold the family together. Splitting them this way is what makes the structure durable. Kris Kluver works with families on this exact distinction at thethirtyadvisors.com.