I don't believe an accident of birth makes people sisters or brothers. It makes them siblings, gives them mutuality of parentage. Sisterhood and brotherhood is a condition people have to work at.
Women opened the windows of my eyes and the doors of my spirit. Had it not been for the woman-mother, the woman-sister, and the woman-friend, I would have been sleeping among those who seek the tranquility of the world with their snoring.
With a basic understanding of all humans as brothers and sisters, we can appreciate the usefulness of different systems and ideologies that can accommodate different individuals and groups with different cultural heritages, having different dispositions and tastes. Each person has the right to choose whatever is most suitable, on the basis of a deep understanding of all others as brothers and sisters.