When Al leaned into his embrace, Severus' hands rubbed slow, hopefully soothing circles on Al's back. Severus' reaction to Al's memory of Lily was a pang of wistfulness; inwardly, he thought he knew now which member of Al's family had contributed the most toward his experiences of laughter.
Severus never really knew Al's sister; indeed, he had spoken to her only once, before the baby had been born. He shared that memory with Al, since it was all he had of her to share.
He lingered in the contact, a quiet, undemanding presence, offering acceptance and understanding, a listening ear with no judging glare to counteract it. He would not be the one to break it; he would give Al all the time he needed.
None of his Headmaster duties were anywhere near as important.