Alex wasn't sure exactly when Ethan fell asleep but he started leaning on his shoulder shortly before the credits started rolling. This was surprising because of his endurance training. Even if he still had another five years to go before he was considered full-fledged, he should still be stronger than this.
Claire wouldn't think that way though. First and foremost she thought of the Numbers as human. Humans had weaknesses, such as falling asleep during movies.
He tried to think of this from the perspective of a normal person. Children were generally considered weaker than adults; he had seen it for himself when they were ice skating. They held onto their parents' hands or were advised to stay close so they wouldn't get lost.
Alex didn't know much about how children were 'supposed to' be other than that. Maybe he should ask Claire later. His childhood in the Agency hadn't allowed for any sort of weakness whatsoever.