Database Structure

I have what should be a very dumb problem, but i keep questioning myself on the best way to fix it. So i thought id throw it out to y'all and see what comes back.

I have 3 tables. Clients, Projects, and Lists. There is a one to many relation between Clients and Projects, and Clients and Lists.
That is to say that a client can have multiple projects and these projects can use any or all of his lists.

This works fine, the wrinkle comes in when i have a client, who has clients who have their own lists.
I treat this just as a client with different projects, but the lists now need to be associated with this project only, and no longer with every project that this client has.

Should I create another table to handle these exceptions? or is there a more elegant way.

TIA
Chad