If It Makes You Happy (слэш)

Written for dresden_kink round 4 for the following challenge:
Marcone hates the thought of Harry being in a relationship with Thomas. Mainly because if he had Harry's attention he'd never let him go. It drives him insane that Thomas just doesn't seem to care that much but Harry seems to love him anyway.
Marcone concocts a plan to make Harry happy--by making sure Thomas makes Harry happy--no matter how much it pains Marcone to do so. If/when that doesn't work there's always the last resort--steal Harry away to do it himself.
Bonus if Harry is completely attached to Marcone and finds his machinations cutely endearing/baffling/disturbing/irritating.