Ethnicity question

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Ethnicity has always been an odd tick Box on forms for me. I am mostly white but my mother is mixed (half white). You can tell that myself and my sister have a little of something “other” but as I’m mostly white I always tick white on ethnicity. Now I am not so sure if that is the correct answer 🤷🏻‍♀️. Are there any other people here who has this issue also? What do you tend to do?