It's terribly complicated. Let me tell you, siblings definitely do not consider themselves unrelated when they've been working together in business. If you now look at section 84.1.... I understand that in that section family members are related. The reason we make them related there is that we're so worried that family members are just trying to game the system.
Can you share a story with us in which a family sold to a stranger because they couldn't afford the tax hit of selling to their child?