To some people, parents are their world, even after they've grown up. This is why the terms momma's boy and daddy's girl have been carried on and used even later in life because there are some people that go beyond the level of maintaining a respect and reverence for their parents into their older age and still think of them as mentors and as friends. While this is a sweet concept it can also be a very sad and debilitating one.
The interpretation for a dream of dead parents or the death of a parent is determined by your relationship to your own parents, as stated earlier. It should go without saying that if you were always wishing for your parents to die as a kid and just now they finally did in your dreams, that you might be having a happy dream, and it should also go without saying that someone should be devastated if they loved their parents dearly and they died in their dreams. These dreams can sometimes just be an indication of how you are doing in your life, generally happy or generally depressed. However these dreams can also have less vague meanings.
If you were close to your parents and had a dream that your parents died or that one of them died then this usually means that some sort of support that you had been getting has just recently been cut out of your life. Perhaps you were getting child support payments or you were being held together by a close friends words emotionally speaking, and that close friend has just gone away. There are a lot of reasons that you might have a dream in which your parents died if a strong arm of support in your life has just exited out of it because this is what parents represent. They represent support and the ability for you to get on well in life while being able to lean on the shoulder of someone else when you need the help.
There are many different parenting styles though and not all of them are positive. For example you might have had parents that were abusive or that discouraged you when you needed them to have confidence in you. If that is the case then this explains why you might be dreaming of them dying. It means that you have gotten rid of an oppressive and unsupportive influence over yourself. You no longer have to worry about anyone bothering you or about anyone influencing you to do something against your will. Of course there are a multitude of unsupportive influences that a person might have to deal with. It doesn't mean that your parents have been taken out of your life. They may have already been taken out of your life some time ago. These things are just symbols. This could just mean that you are dealing with anyone in your life that is unsupportive or neglectful and your parents are just standing in as a symbol for them. When you dream of dead parents it just means that you don't have to be stressed by someone with negative views or unsupportive views. You have gotten them out of your life and you no longer need to worry about them. This is a great thing for you. Be happy about it and celebrate your newly discovered life of freedom.