Since when is a white guy a brother to a black guy

In the Star Trek episode "Whom Gods destroy" kirk says that the leaders of the Axanar Peace Mission had a vision which spread across the galaxy and made him and Mr. Spock brothers.

But they are supposed to be biological, not figurative, brothers in this show.

Fraternal twins happen when two different eggs are fertilized by two different sperm at about the same time. If a woman is slutty enough her eggs could be fertilized by two different men at about the same time and her twins would have two different fathers. A few decades ago there was a case in Germany where a woman gave birth to fraternal twins, one "white" and one "black", believed to have different fathers.

In societies with harems royal half brothers might look like they belonged to difference races due to the difference races of their different mothers.

But the kings in this show are supposed to be full brothers, not half brothers, and share the same father and the same mother.

However, a person can have a much more mixed ancestry than you can see, and thus can pass on to his or her children a much different appearance than you would expect. Every one has positions for two parents, four grand parents, eight great grand parents, sixteen great great grand parents, and so on.

Each of a woman's eggs has its own genetic mixture, a subset of her total set of genes, which is never identical with that of her other eggs. Each of a man's sperm has its own genetic mixture, a subset of his total set of genes, which is never identical with that of his other sperms.

Thus it is perfectly possible for two different sperm from a husband with two very different sets of genes to fuse with two different eggs from the wife with very different sets of genes and produce fraternal twins who are full brothers but look totally different, even like members of different races.

You might want to look up the H.P. Lovecraft story "The Dunwich Horror" for an example of brothers who look radially different. And there is the Philip K. Dick science fiction story "Oh, to be a Blobel!" in which a Human marries a blob-like alien Blobel and some of their children are Human, some are Blobels, and some are hybrids.

Those stories are fantasy and science fiction, but they are based on the sound biological princible that full siblings can have radically different genes and appearances.

well in Great Britain one child is completely white while the others have a range of darkness.

There father is black and there mother is white.

The child that is white looking his a twin to his black brother

The premise is that they're fraternal twins. Mother is black, father is white. They came out one black, one white. Chill out.