I agree. Though, a lot of animes have different styles. You can't tell me Kuroshitsuji/Black Butler has the same style as Puella Magi Madoka Magica/Mahou Shoujo Madoka Magica.
However, the only Square Enix Characters that really look alike are meant to look alike.
Ex: Tidus/Shuyin (Dream of the Fayth), Yuna/Lenne, Rikku/Yuna (cousins), Cloud/Lightning (Toriyama wanted a female Cloud in FFXIII), Lightning/Serah (sisters) Lumina/Lightning/Serah(Lumina harboring Serah's soul and personified Lightning's feelings), Reno/Lea (Nomura wanted a Reno like character in KH), Kadaj, Yazoo, and Loz/Sephiroth (Sephiroth fragments.) And sometimes, I believe Nomura likes a character so much he draws another similar to it Sora/Cloud
Kairi/Namine have the same model they just have a palette swap and hair style change because Nobody/Somebody relationship.