The Black community seems to be misguided about polygamy and what a sister wife is. First off a sister wife is not for the sexual benefit of the husband. She is added to a relationship to help share the responsibility, of growing and maintaining the family.
The sister wife relationship was started by our African women ancestors who saw that villages was struggling from a lack of men whether it was due to war, sickness or more female births. In order to meet the needs of the single African women and lowering adultery and competition, the elders got together and decided that the black men could have more than one wife if he could take care of them. This also helped to keep the women sisterhood. Sister wives share in the responsibility of growing and taking care of the family.
I have been in search of a sister wife for a while now and to my surprise have found women who were only interested in sex. This blew my mind.