After Harry has killed Voldemort Brother Z appears to him and explains some things. After Harry sweeps through the Ministry he disappears – to 1981 and becomes Brother Z.
The following autumn Snape returns as teacher, Hermione is Transfiguration assistant and cares for her blinded lover Luna and Brother Z becomes also at teacher at Hogwarts. Harry manages to heal Lunas wounds and helps her regain her sight. On christmas he reveals his secret to the two of them and they become involved. Harry has also a daughter at Beaubatton. At the end of term Snape leaves for good – blinded and diminished in life and magical power.
DrT writes himself:
The Final Battle is over. Harry has left Britain, leaving a devastated magical community, a lost Hermione, and a blinded Luna. Hermione becomes Professor McGonagall’s apprentice while she cares for Luna. She also has to deal with Snape, who has managed to worm his way back into Hogwarts, and the mysterious Brother Z.
The story can be read online at FicWad.
As usual there is also a PDF.