12 Grimmauld place is Sirius' house. When he dies, Harry inherits it, along with Kreacher the house-elf..Sirus' House.Number 12, Grimmauld Place is the ancestral home of the Black family of which Sirius was the last surviving male heir. It is unplottable and cannot be seen under a fidelis charm. Sirius offered it as headquarters for the use of the reunited Order of the Phoenix when Voldemort returns. The family was pure-blood and into dark magic which resulted in a number of nasty magical objects around the house that needed to be cleared out. Excepting Sirius, they were arrogant bigots who supported Voldemort's rise to power. The family tree on one long wall included burnt spots of pictures of family members who didn't toe the family line. Sirius Black and Andromeda Black Tonks, his cousin, were two of those burnt off. Harry inherited it from his godfather Sirius along with the resident house elf Kreature.