when a person dies while having bitcoins on his or her wallet, it is still there and nobody can have access to that.  It will still remain on the dead person's account and will not disappear unless some people have taken it. But it is can be prevented, whether your account has more or less money,one of your family member or one of your loved ones need to know the password of your account so they can access the dead person's money on its wallet. The money will be stucked there unless external interference takes place. The bitcoins that are remained in the account are considered now worthless if not used because it will not be part of circulatuon.