In Grave Peril Leah made a couple of deals. One with Harry in the graveyard, and one with Susan at Bianca's ball. In both cases she kissed them when the deal was made. Thomas had a wound on his neck, and Harry asked him what had happened. Thomas said that Harry's godmother had given him a kiss. I find it curious that she'd have done that if not for deal making. Perhaps it was for his first born, and Thomas assuming he'd never have children accepted the deal.