Interesting first HP fic! It feels like there is a lot of backstory to this particular brewing process, or that this is hinting at a lot more:
From what he understood from the healers, Harry Potter was neither kith nor kin. The expression on the boy's face, when they had first met, had contested to that. He could still remember the way Harry had awkwardly clasped his hand, staring at the floor as he did so. Snape had been tempted to release weeks of pent-up bedside vitriol on the boy until, suddenly, Harry had jerked his head up and looked at him straight in the eye.
Afterwards, Snape would note that Harry Potter indeed looked nothing remotely like him. And that there really was nothing unique about the boy's green eyes.