No, not unless the classes themselves define such a way (via a method or a property.)
Suppose instance A1 of class A has an instance of class C stored as a private property, intended to be accessed only by methods of class A and not by users. Granting users unrestricted access to that contained object of class C could render A1 no longer a valid instance of class A, if class A further restricts the values properties of class C can take.
For instance, consider class A representing an Outlook meeting invitation. It has a property representing whether a meeting requires videoconferencing (abbreviated from now on as VC.) It also has a property of class C representing the room in which the meeting is to be held, and the rooms have a property indicating whether the room is VC capable. Meetings that require VC can only be held in rooms that are VC capable. If you can change the VC property of the room stored in the meeting invitation class without going through or informing the invitation object, you could end up with a meeting that requires VC but is being held in a room that is not VC capable.