Looking for a cartoon or anime that I heard about in passing a few years ago or so, I think it may have been a space cop show, it was definitely sci fi I think, and the most striking thing I remember was that I think it was known because the series ended with the protagonist finding out one of the rivals/enemies/antagonists was actually her sister and there was some twist at the end. The characters may have been anthropomorphic but I can't recall clearly. The only thing I found that rang any bells while I was searching was Tamala 2010, but I don't think it's the same thing after checking it out.

For other stuff that brings loose associations to my head on it, I think it may be known for having inspired some trigger show like Panty and Stocking or maybe space patrol luluco or something, and I think stylistically it may have been a blend of western cartoons and anime like super milk chan's art style.