One of my headcanons is that Vinyl Scratch is her daughter, because of the somewhat similar resemblance and love of music, but I have seen some theories where Torch Song & Coco Pommel could be her kids too, because I will admit: they do look more like Sapphire than Vinyl does. Or maybe they're all sisters?

I dunno, man. Just thinkin'.

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From what I can tell, Sapphire, Vinyl, Torch and Coco are all separate ponies with no relation to her whatsoever. Besides, they appear to be around the same age, with Sapphire and Torch Song older than Vinyl and Coco, but not that old enough to make them their daughters.

So, this theory is unlikely. But let's see if you can make it work.