Merlin wasn't jealous but did feel a little ache for that sense of family that he got from the place; not that he hated his own, but it would have been nice if everyone had been able to get along.
He didn't really think down that route, and allowed himself to be distracted by the fact that Zach hadn't let go of his hand yet instead; he didn't know how to pull it back without looking like a jerk, so he let it stay although he was very conscious of the feel of Zach's skin pressed to his.
He looked over the horses feeling a little out of his depth. "I used to." he advised. "When I was younger." Before Hogwarts in fact.