Like a color palette, from just a handful of original citrus species has resulted all sorts of new families, each with their own unique character.
Repeatedly backcrossing a pomelo with mandarin resulted in the common Orange. And the flavor is not quite the same as either of its original ancestors. All that selective inbreeding eliminated nuances in flavor and resulted in high levels of Valencene.
Cross an Orange again with a tangerine (mandarin) and you get a Tangor.
When a Pomelo that had been brought to Jamaica inadvertently hybridized with Orange and the resulting offspring, which had small sour fruits that grew in clusters like grapes, began spreading in the wild, that was the start of the lineage that today is known as grapefruit. And grapefruit, while similar to pomelo in many respects, also has its own unique flavor differences. It developed very high levels of the pungent sweet compound thioterpineol, the most characteristic component of grapefruit aroma.
Cross a grapefruit with a mandarin and you get a Tangelo (which really does taste like a cross between mandarin and pomelo).
Cross a tangelo with a pomelo again and you get a Tangelolo.
These are all just varying combinations on a spectrum between mandarin and pomelo, yet each family is unique and has its own taste.
Cocktail Grapefruit was a hybrid between grapefruit and mandarin, but is still considered a grapefruit.
And what if you cross a grapefruit with a pomelo? Oro Blanco is conveniently easy to categorize as a grapefruit because its pomelo parent happened to be Siamese Sweet, which did not have much flavor of its own to contribute. So Oro Blanco mostly takes on the grapefruit flavor of its Duncan parent.
There are so many potential combinations. What other new families could be possible?