Probably largely his nature, but I like to think it's also a sign of secure attachment to his parents and caregivers. (askmoxie.org)
This is an introductory summary of a full paper which presents a critical review of the research literature on the relation between attachment to parents during adolescence and psychological and social adjustment. (cyc-net.org)
Creating a healthy attachment to a parent does not happen instantly. (babycenter.com)