[SoothingDave]

Thanks for clearing (?) that up. I can see the advantages of monogamy here and can also see why a catch-all use of "brother" would come into play.

SD

[malakhi]

I can see the advantages of monogamy here

I don't think its just a matter of monogamy. Before the advent of modern medicine, many women died in childbirth, and both men and women had a high rate of death due to infectious diseases. There would perforce have been far numerous cases of half-siblings.