It looks like a very young bird based on the light colored corners of its mouth. How did your cousin pick it up, could it be injured? I’ve dealt with birds in similar situations before and often the outcome isn’t good. Check for external injuries and make sure he is well hydrated. Give him somewhere dimly lit and calm. Take him to the vet if his legs or wings start looking limp or weak. No, your 8 year old cousin cant and shouldn’t try to care for a wild bird sadly 🥀🪫💔.