Soroptimist:

A member of an international organization of professional women and businesswomen that promotes public service

Sororate (n):

1.      The marriages that take place when men have two or more sisters as wives after the first wives have been found to be barren or after their deaths.
2. Marriage to a deceased wife's sister: "Some societies have sororate as a custom when a widower marries a younger sister of his deceased wife."

sororize (, sororizes; sororized; sororizing):

To associate, or to hold fellowship, as sisters with each other; to have sisterly feelings with other females.