I like Adeline as much as Sophia, but I don't think it fits stylistically with Lauren and Katelyn the same way Ava or Sophia does. If you plan to call her Addie, though, I think that fits quite will with big sisters' names. Though honestly, I don't think Adeline is sufficiently unlike Lauren and Katelyn to stand out a whole lot -- and if you and your husband like it best, use it!