In India there used to be a custom called Sati, by which a wife who was devoted to her husband was cremated with him. Some people felt a great horror at the idea, but others thought differently. I would say in regard to this question that when two souls have become one, whether they are both on earth or whether one of them has gone to another plane, they are still united. If one of them remains living then that living person is as though dead here, for he only lives there where there is real unity. There is no separation. Nothing can separate two souls if they are really united.