Periodically update your estate planning.
Apparently Heath Ledger wrote a will in 2003. He had it lodged according to Australian law.
Only one problem... he became involved with Michelle Williams and had a child with her in 2005.... and he did not update his will.
So when he died, his will still named as his heirs his parents and his sister. And his daughter would have gotten nothing.
Fortunately, Ledger's parents are mensches and have stated that they will make sure that his daughter, Mathilda, is taken care of and not cut out. Otherwise, it could have become an ugly court fight, as it sometimes does.