I think mixed race relationships are much easier and more common these days than they were, but something still lingers.
I am from a mixed race family, and it was very common in the early 80s when out and about with my Mum for people to not twig that we were related - at the supermarket they wouldn't ring up goods I'd put on the conveyor belt next to my Mum's because they thought I wasn't with her.
I'm in a mixed race relationship myself, and haven't had any problems or comments in this country, though people have eyed us disapprovingly when on holiday. But, at my DS's last weigh in with the HV she asked whether I was his Mum or not
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But, the point I came on to make was, I don't really understand why people think life is more difficult/complicated in a mixed race relationship (DH's Mum made the same point when we first got together, and thought our children would have things harder). It's not like that at all, or at least not in my experience. Do people who marry within their own races really marry people whose backgrounds are identical to their own? Unless you marry someone from your town there are always going to be differences. The biggest difference between me and DH isn't race, it's country bumpkin vs city slicker.
Sorry this is long. I could go on about this all day...