Fate/stay night: Children of the Magus Killer

The Holy Grail War pits master and servant against master and servant, and in this fifth conflict, two of those masters are actually siblings. For those who already know who they are (or for those who simply don’t care), click the logo above or click here to see them.
From the anime series Fate/stay night

Cross Ange: Rondo of Angel and Dragon: In Transit

In the backseat of a vehicle, Prince Julio and wheelchair-bound Princess Sylvia face Princess Angelise

Prince Julio Misurugi and his younger sisters, Princess Angelise and Princess Sylvia, are members of the royal family in the seemingly peaceful Misurugi Empire.
From the anime series Cross Ange: Tenshi to Ryuu no Rondo (Cross Ange: Rondo of Angel and Dragon)

Undefeated Bahamut Chronicle: Ex-Royalty

Airi Arcadia stands next to her bemused older brother, Lux

Lux Arcadia and his little sister, Airi, are a former prince and princess of the overthrown Arcadia Empire.
From the anime series Saijaku Muhai no Bahamut (Undefeated Bahamut Chronicle)

The Seven Deadly Sins: Long Time No See

Harlequin and Elaine facing one another

Harlequin and his sister, Elaine, are the protectors of the fairy forest.
From the anime series Nanatsu no Taizai (The Seven Deadly Sins)