During periods of mourning, the high priest was not allowed to leave the sanctuary compound. This was done so that no impurity might defile the high priest, hindering his service in the Tabernacle. Leviticus 21:12 does not mean that the high priest lived in the sanctuary, only that his duties there took precedence over family ties, even when his parents died.
12 Il ne sortira point du sanctuaire, et ne profanera point le sanctuaire de son Dieu; car l'huile d'onction de son Dieu est une couronne sur lui. Je suis l'Eternel.