Cyclops Shoujo Saipu: The Tall And Short Of It

Fuuka Saitou lovingly wraps her arms around her much shorter but beloved big brother, Hikaru

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


Medaka Box: The Early Years

Maguro Kurokami and his youngest sister, Medaka, try to comfort Kujira, their misanthropic middle sister.

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

Shakugan no Shana: Deep Love

With Tiriel clinging to Sorath's shoulder, she and her older brother defiantly face forward

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

Sundae with a Side of Love

Happy Valentine's Day from Sister/Brother Complex featuring Sorath and Tiriel from Shakugan no Shana

Image from the anime series Shakugan no Shana

Rozen Maiden: Mitf├╝hlend

Nori Sakurada smiles while her younger brother Jun facepalms

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

Non Non Biyori: A Warm Welcome

Eldest child and only boy Suguru Koshigaya stands with his hands in his pockets. Youngest sister Natsumi holds the door open. Middle sibling and eldest sister Komari Koshigaya stands with both hands at her sides.

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