It's interesting you mentioned this. My aunt and uncle were conjoined. They were brother and sister and actually married each other for lack of a better arrangement. They had 3 children who weren't conjoined and when my uncle passed, it was only due to the fact that they were legally married that he was allowed to leave his estate to my aunt and set up a trust for the children. Funnily enough, one of their children, my cousin, later gave birth to a set of conjoined twins.