Sisters have great privileges among these Indians [of the Plains]. All the horses which a young man steals, or captures in war, belong to them. If an Indian returns from an expedition on horseback and meets his sister, he will immediately alight and give her the horse. On the other hand, if he wishes to possess some object of value belonging to his sister, for instance, a dress, he goes and abruptly demands it and immediately receives it. Even if it should be the very dress she is wearing she will take it off and give it to her brother.²

But among the Hidatsa,

as among the Crow, it was not considered proper that an adult brother and sister should hold long conversations together. "If I am married," said Buffalo-bird-woman, "and Wolf-chief visits me with his wife, he talks with my husband and I talk with his wife. If he should come to my house when I am alone, we should settle any business or say anything special we may have to say to each other and then he would leave."

This in no way interferes with their sentiments. "I love Wolf-chief," said the same informant, "and he loves me. I have nothing against him in my heart." She always tries to help him and vice versa. When she was little, she took care of him. If he did anything wrong, she scolded him, and if she did anything out of the way she was scolded by him. Until she was ten years of age, they slept together, but later they slept separately and from that time on only spoke to each other when necessary.

Black-horn gave Buffalo-bird-woman many horses, while she gave presents to his wife.

A woman would tan her brother’s robes and prepare meals for him. He would exhort his sister not to do anything bad. Neither will say anything suggestive of obscenity in the other’s presence.

When there is a dance at which presents are distributed, a sister will ask her brother to give away her own horses. On one occasion Buffalo-bird-woman’s brothers thus disposed of seven of her horses.³

There is, however, no known group in which marriage is approved between brother and sister if we except some cases where such marriages were undertaken by dynasties for the preservation of the royal blood (Egypt, Sumeria, Peru, Hawaii, etc.), some cases of African chiefs who are "above the law," and some technical evasions to be mentioned later. The older reports of such marriages among tribes of low culture, for example, the Veddas of Ceylon, have been disproved.¹

²Wied, M.vonn/an/an/an/a, (ed. Thwaites), 2: 281–282.

³ Lowie, R. H., "Notes on the Social Organization and Customs of the Mandan, Hidatsa, and Crow Indians," Amer. Mus. Nat. Hist., Anth. Pap., 21: 38–39.

¹ Seligmann, C. G., The Veddas, 66.