Public Groups under Private?

I feel like I'm just trying all the wrong searches, but simple question: If I have 2 "public" sub-groups under a "private" group, are the public groups accessible to anyone outside of the private group membership? Or are they private because of the parent?

The explanation: A group that needs some level of privacy has 2 sub-groups that share members. They don't want to have to approve membership to 2 sub-groups, and would rather administer it through just one.

Thanks!