well actually he will never lose completely his flexibility because he was born with hypermobility syndrome... regular people can also become very flexible but not like him, it means there will be chronic adaptations in your body because of the stimuli generated by stretching and joint mobility exercises... just like his body will never be stiff like a non-born-flexible person who never traines flexibility skills, a normal person will never be flexible like him because of genetics.... but as i said before, everything is possible with hard work and proper training... respecting ones individuality, and practising safely, always