Yes (but be careful of context). To use C++ terminology, an object (not a reference) is defined to be an instance of exactly one class (in classical OO), called its most derived class. An object not directly contained in any other is called the complete object [Stroustrup 90]. An object is a member of several classes, including all of the classes its declared (or most derived) class inherits from. With static typing and inclusion polymorphism based on class, if a polymorphic object (or reference) is made to refer to an object, that object must be a member of the polymorphic object's class.
This also provides a good example of differing definitions among object- oriented languages, since a member is defined as above in CLOS, but a member of a class is one of its instance variables in C++.
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