What returns a DAO?

Lets suppose that I have two classes Foo and Bar with each respective DAO.

Lets say that a foo has many bars.

So the method that returns the bars of a foo where should it go?

class FooDAO
  def bars_from_foo(foo)
    # return the bars of that foo
  end
end

class BarDAO
  def bars_from_foo(foo)
    # returns the bars of that foo
  end
end

My doubt is, does FooDAO only return foo objects? Or does FooDAO only include the methods that a foo will need?

In my opinion, I choose the first one: FooDAO only returns foo objects. Because, the method could be used from another class, that has nothing in common with the other DAO. I can't think in an example right now.

I would like to read some opinions from experts.