Actually, DOM parsers alway use a SAX parser as input and constuct the DOM as the various SAX events arrive. Take a look at the
Java source code to learn how it is done.
I don't understand what your problem "who is the parent" etc is. A DOM has a Document node containing all of the DOM data. Your first step should be to thoroughly understand the contents of the org.w3c.dom package - there is a great table in the javadocs for the Node interface that will help you understand the contents of a DOM.
Bill