Don't forget marriage is only half the story. Most people don't marry these days and just enter, sometimes unintentionally, defacto relationships.
Some also have mistresses and/or menstresses which may also qualify as a defacto even though someone is married. Under the NSW Succession Act it takes this into account. So if you are separated but not legally divorced, or you have a lover on the side then take care.
For Exhibit A - See Richard Pratt