Hindu marriage act 1955

If you mention that as a reason then the other party has to either deny or accept it, if so it will be a contested divorce and a mutual consent divorce.

Don't create your own unnecessary concept and make simple things complicated to suffer more due to your adamant thoughts.

You mean to say the marraige is not consummated ,and for that reason your son wants divorce. But you have to show that the marraige is not consummated due to his wife and it can never be consummated then that is good ground for divorce 

In mutual consent divorce petition, no any allegations  are made on party to petition if any allegations  are made then it will be contested petition and consent petition, simply it is mentioned that both the parties are agreed to get divorce.