Yuuta and Yumeha look like brother and sister but Kuzuha looks different, hair style and color. Makes me wonder if they might pull the non or half only blood relation thing bringing her into the harem. Or maybe it's just wishful thinking on my part since I have a thing for Kuzuha.

Pretty sure your wishful thinking is shared by most of the fanbase.

Well their eye colour is the same, and asians tend to have black hair so you can say that Kuzuha looks the least like their mother.

>Kuzuha is an anime only character.
Oops, it seems she was in the novels as well.

Artist Commentary

10/27/2012 17:34 565×800 SAI

おーい樟葉お茶とってー

樟葉「洗いものしてるから自分で取ってー」勇太「いやっ俺も黒の書物読んで・・」樟葉「えっ？・・・」勇太「あ、いやっ！夢葉がさぁ～離してくれなくて・・・」夢葉「ｷｬｯｷｬｯ」樟葉「んもぉしょうがないなぁ～」

I don't get it, what harem. Chuuni had a pretty cut-and-dry thing between Yuuta and Rikka, cutting off the Nibutani route relatively early and not really introducing any other love interests through the rest of the story.