We never thought about race
But I bet you did. Children, adults, nobody can NOT think about race. You can not talk about it, but you can't not think about it. It's not bad to think about it, it's great that different people come from different parts of the world, that their families celebrate different holidays, eat different foods, have different family traditions, and part of those differences includes differences in appearance.
Tea what is wrong with describing my child's skin tone in those terms? I could tell you all we know about my DC's background, but a) that's the DC's story to tell and b) it would totally out me. How else am I supposed to describe my child's skin tone? Or am I supposed to pretend that my DC is white? That nobody will notice that one of my DCs has a different skin tone to the other one? The information about not having a Black African background was for context in this particular thread as it means that my DC won't have quite the same experiences as either my adult friend with Jamaican heritage, or the OP's children with Black heritage. I'm not quite sure what you're getting at here. The fact that I gave some information about my DC's heritage? Or that I indicated something about this DC's skin tone?
Am I allowed to say that my other DC burns easily in the sun and has very pale blue eyes? Or is it wrong to mention skin colour, but OK to mention eye colour? Can I mention that my other DC appears White British but that is not their heritage?
I can tell you that my older DC has already noticed that the two siblings have different skin tones. And if I say "shush, don't notice that, we don't talk about that, we aren't allowed to think about race" then what I am saying to my DC is that it is shameful to talk about their skin colours.