College student Hikaru Saitou is not amused when his middle-school-aged little sister, Fuuka, grows considerably taller than him.
From the anime series Cyclops Shoujo Saipu
The Kurokami siblings are all geniuses. Oldest child Maguro realizes his analytic brilliance in the process of trying to help one of his two beloved younger sisters. Kujira, the middle child and eldest sister, willingly lives a deprived, isolated life of nothing but studying and experimentation in order to become an expert on biology, whereas youngest sibling, Medaka, is an all-around prodigy who can excel at essentially everything she sees.
From the anime series Medaka Box
Sorath / Aizenji (He Who Loves Himself), despite being the older sibling, acts more childish and carefree than his devoted, protective, and mature younger sister, Tiriel / Aizenta (One Indulged in Love of Others), but both are quite serious about consuming the Power of Existence of humans to survive.
From the anime series Shakugan no Shana
Image from the anime series Shakugan no Shana
Nori Sakurada takes care of her rude, arrogant, and insecure little brother, Jun, to the best of her abilities while their parents are working overseas.
From the anime series Rozen Maiden
The Koshigaya siblings are good people. The eldest child, Suguru, is a man of few words who lets his actions speak for him. Komari (on right), the middle sibling, may be physically short and dislike it when people point that out, but she has a big heart. Finally, there’s Natsumi, the carefree, playful, back-talking, bad-at-school youngest sister. She keeps things interesting.
From the anime series Non Non Biyori