Re: Prayer for disobedient child
Leave the child alone for some time, because there is no use of forcing him to do anything at this age.
First, tell the parents to do dua for him with tears of sincerity at the time of Tahajjud, do alot of sadaqa, fulfill all the "basic" orders of Islam, repent for their past sins infront of Allah, think if they had ever violated anyone's rights or hurt anyone's heart ( If this is the case than they should immediately go to them and beg them for forgiveness and return their rights)
p.s. I am saying all this because once I was even worst case than that guy (interms of manners) My parents did all the above due to which Allah blessed me with guidence to become relatively better than what I was before.
The heart of every human is in the control of Allah, and Allah bless an ignorant person towards the right path when his pious relatives beg for it infront of Allah.