For iCloud Photo Sharing: does anyone know how to unsubscribe from someone's photo stream without them knowing I've done it?

I have a distant family member who just had a baby and they invited me to join the photo stream. It would have been rude to decline so I went ahead and accepted. But at this point they're posting dozens of pictures a day and I don't want to see them any more.

I've turned off notifications, but I don't want to see the album in my list of photo albums either. If that makes me a dick, so be it. I want to leave the group without hurting anyone's feelings. Like un-following someone on Facebook without them knowing.

I was going to post this in High-Tech but figured I might be more likely to find an answer in here. I also Googled this of course, but no dice.

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