You really have to get into the show in order to get all of the siblings straighted out . . . for the longest time, I kept getting Lori and Leni mixed up (because they're the two oldest blonde valley girl sisters), as well as Lana and Lola (because they're the twins), and, if you can believe it, even Luan and Lynn (both immature brunette sisters with ponytails). Having said that, while I still wouldn't say this series is perfect by any means, it has gradually gotten better over the years, despite what the consensus of the fandom may say . . . if anything, I would say (and this is an unpopular opinion) the series has actually come into its own after Chris Savino was fired - by that time, the writers really stepped up to the plate and further fleshed out the characters and added so much more layers and depth to them, whereas under Savino's supervision, yes, there was some character development (especially after they shifted the focus off of Lincoln and the sisters weren't so flat and one-dimensional anymore), but it was still mostly a gag comedy show.
I will also say that I think it's pretty neat that Nickelodeon actually allowed them to age the characters up and bump them up a grade in school (except for Lynn, for some reason), which further added to their growth and development (considering this is the same studio that Joe Murray had to fight with to get Filburt and Dr. Hutchison married because they didn't like character development) . . . see, if ARTHUR had done this, maybe, maybe that show wouldn't have gotten as stale and tired as it has been for the past several years
I will also say that I think it's pretty neat that Nickelodeon actually allowed them to age the characters up and bump them up a grade in school (except for Lynn, for some reason), which further added to their growth and development (considering this is the same studio that Joe Murray had to fight with to get Filburt and Dr. Hutchison married because they didn't like character development) . . . see, if ARTHUR had done this, maybe, maybe that show wouldn't have gotten as stale and tired as it has been for the past several years