Ma'an family because of a marriage. That and because the male line of succession came to an end. There is no complete name for Mrs Shihab-Ma'an but it is what is needed to link two families and to link the succession of power.
When you consider history, it is often told through the conflicts and the succession of office holders (Fashr-al_Din II and three of his sons were execured).. It is not only what shaped history, the relations through marriage prevented many conflicts and allowed for cultural development in times of peace.