To be speaking in terms of made for each other flows neatly from their recitation of poetry, though it's certainly a bold step, particularly for a man like Holmes whose relationships have been few, but Holmes isn't like Mycroft, whose logical mind drives him away from society. Holmes is a confused mix of logic and emotion, which occasionally drives him to brief periods of madness, and it results in relationships which are as emotional as they are logically defined. Has he considered that he and Watson were made for each other prior to this? He thinks so, as the notion is hardly surprising to him.

"You are made for me. Nature's own hand has fashioned you out for me, for my love and my pleasure," he murmurs, his tone a jumble of things: an attempt at romance, the rasp of his lust, and the rumble of his own emotions. He kisses Watson again as he adds a second finger, encouraging Watson's legs farther apart with his knees, wanting more of him.