I haven't thought of this fic in ages and no idea where I read it: It was early on and Angel was 'greyer' than cannon. Spike is staying with him and Xander turns up at the beginning of the story to ask Angel for info on a child-eating demon. They can smell Xanders attraction to both of them and Spike starts to keep an eye on him - buying him food and making sure his parents don't hit him.
Spike offers Xander a bed at Angel's place and one night when his parents are fighting he accepts. Xander spies on Angel and Spike screwing and Spike seduces him into naughty touching. Angel tells Spike he should be the one to seduce Xander but he wants to watch.
It ended WIP with the the two vampires bionking on the stairs outside Xanders bedroom
anyone know it?