When people are brothers or sisters, they would share the same kind of genetic patterns that mark them as “siblings”
For example the people of the northern hemisphere like Nenets or Chuckchi. Another example would be Polynesian people.
But I think you mean that in a more religious/social/political way.
I can understand that people search for communion and we live in a time where many people lost the connection to their families and also their cultural and biological heritage.
But I don’t think that it has a positive intention to unite people, that are not really related and create an origin story, that has no support in reality.
You can find always similarities with people because you have a shared social or religious intention, but that doesn't mean that you must be of the same biological kind.
In the past ideas like white, red, black and yellow race where spread, but this ideas where build on social ideas, not science.
And humans tend to search for their social ideas in science, not the other way round.
With the anthropology of the last century, the diversification of racial classification took place and finally lead to the complex systems of today, that can differentiate more accurate.
The stuff Coon did, is outdated today and no more really accurate. This is like doing planting crops today with the technology of the middle ages.
There are many Indians, Australians and Middle Easterns who would disagree with your idea that they are all part of the “Black” movement.
But there are also people that would agree, because they hope for asocial advantage because of a unity of people who share the same skin color. Or they are like you and believe in the mythology of the idea of an ancient black world.
In many parts of the world people still believe that they are all descended from two people in the middle east, also a weird idea in my opinion, but it is an emotional thing, in my country such ideas are protected by law. But that doesn't make them real.
When I would have to say what are the brothers and sisters of the ancient Sub Saharan Africans, I would say the archaic humans of Eurasia. They have the ancestral African ancestry components, they looked similar to them in many traits from what can be seen in the DNA data. They where also Hunter Gatherers, but we don’t know how exactly their culture was like.
In that sense Europe and whole Eurasia was once black, because it was populated by those archaic people.
Indians or Australians are in my view based on the data I have seen, different people to the Sub Saharan Africans. They don’t share large amounts of genetic components, so they are not their brothers and sisters. They where a long time isolated from them, like many other ethnic groups and have their own history.
Haplogroups and mtDNA are an indicator for kinship, when they are of the same subclade, but often are just traces of male dominance and conquest, or a relic of early migration. The autosomal DNA, that defines how you look, that also can be used for kinship detection, can differ from the population that once brought the Haplogroups into the population, or founded it. The most haplogroups can be found in different ethnicities and are not limited to only one kind of people.
For example many people of African origin in the US have European Haplogroups. Does that make them white in the view of the social ideas of the USA?
But I don’t think that we discuss anymore about genetics. We discuss here about a social idea, a kind of mythology, an idea that once divided people into 4 races and now into two (White VS POC) and wants to create a worldwide social conflict. Everything that challenges this view of dividing people into 2 categories, must be eliminated, because it challenges the idea of “White VS POC”, it makes the whole conflict obsolete.
This has nothing to do with brotherhood, not with science, but with hate.
While the scientific view of ethnicity has diversified, the social and political views are impoverished.
I am personally cautious when someone calls me brother, often people do this, because they have an agenda and want to instrumentalize you.
You always repeat what you did I the 3 posting before, I always try to show you facts that Sub Saharan Africans and Sout Asians are not the same ethnicity, but you stay at your view point, they are ancient brothers. I stay at mine, they are not. There's no need to discuss anymore, because this will lead to nothing.