In terms of the chronology of the two games, SoTC occurs many years before Ico. The ending shows that (SPOILER)Wander was reborn as a horned child. It's implied in Ico that there are lots of previous horned boys who have been sacrificed, and it's been hinted at that Ico is infact a descendant of the now behorned Wander. So the games are connected, but it's only something you need worry about if you're a fan of both games.