Need help with groups

I need some help with groups… lets say I have 4 groups group1 ,2 ,3 and 4

Group 1 and 2 should be seen by everyone, and they should be able to see everyone.

Group 3 and 4 should see group 1 and 2

However I do not want group 3 and 4 to be able to see each other.

Or should I not create group 3 and 4 at all and just manually add the members to groups 1 and 2 contacts?