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I remember the characters, I think it was a TV show instead, though. An adventure one, American. And I'm confident that it was not Sailor Moon.
OH MY GOD; MY PARENTS ARE GARDENIIIIINNNNGGGGG!!!!!
Princes Gwenevere and the Jewel Riders (or Starla and the Jewel Riders, depending on your country)? I know they all had gems/themes, and two of them were sun and moon. Maybe they had them on their clothes, too. Unfortunately I only had a couple VHS tapes of that, and they didn't match the one you described, but I know there were others!
It's been driving me mad for years but I remember a VHS tape at my Nana's house that had two girls on the front, one was blue or purple and the other was pink. The style was similar to that of Rainbow Brite but I've seen all those movies and none are what i'm thinking of. They were on a stairwell with either a candle in one of their hands or a torch on the wall, they could have been conjoined or just back to back but they looked either like twins or just sister's. One had a moon hairpin and the other had either a star or a sun, It's not Johnny Test's sisters because they weren't around at that time period, especially not on VHS.I was really little when I saw the cover but I'd love to know what it was, if anyone has a clue i'd love to hear it, i'm out of idea's.