My son Behaviour

Hi to All,

I am having a son of 9 yrs old  and a daughter 2 & 1/2  yrs old . My son is so stubborn and he wont listen to us. he watch tv more . he is good in studies , having knowledge by seeing this even my daughter also started like. iam worried even my daughter also becomes like that . can any one suggests how to change my son ??/

cheers

JL