You don't have a reasonable right to privacy of relations. That's all public record.
We should think really carefully about this! My uncle’s right to check out who his long lost cousins could put my genetic information in the hands of a potential employer, insurer, or government. That could be really bad.
This is similar to the Facebook scenario, where it’s not just your privacy you are trading away for whatever benefit, but those of people related or near you.
Btw, I live in Eastern Europe so I'm talking about stuff I've experienced here, maybe in the States or in Western Europe this behavior changed a long time ago and not only recently.
Why should you have a right to block the later from happening? It's not your own personal information.