Dilandau and Jajuka

Spoiler warning: Plot or ending details may follow.

Dilandau Albatou/Celena Schezar and Jajuka.

When Celena is captured by the Zaibach Empire, Jajuka is given charge of her. Though at first he considers it only his duty to look after her, he soon grows to care for Celena, and is distraught that he can't save her from the suffering caused to her by the Fate Alteration Experiments.

Since Jajuka is around Allen's age, it is likely that Celena came to see her guardian as a surrogate older brother, and as a comfort preventing her from being alone, both her and Dilandau's greatest fear.

When all of Dilandau's Dragonslayers are killed, Jajuka looks after Celena while she briefly resurfaces. Upon Dilandau's return, Jajuka informs him of the deaths of his Dragonslayers, telling him he is the only soldier remaining under his control. Dilandau apparently does not recognize Jajuka, but nevertheless trusts and respects him immediately.

While visiting her mother Encia's grave with Allen and Eries, Celena turns back into Dilandau and calls Jajuka. In the final battle, Jajuka intervenes between Van and Dilandau and takes a mortal blow to protect his commander and ward. As he is dying, he tells Dilandau that it's okay to be Celena again, causing her to resurface and Dilandau to presumably disappear permanently.