Today I got a Shocking news

I am on Tier 1 (Entrepreneur) Visa with 3 Dependent Visa (Visa Stamped in April 2013) under my sponsorship as below :
1). My self as main Applicant.
1). Wife - Spouse - Mother of my below mention 2 Kids.
2). Son - Will be 20+ at the Time of Extension Application in May 2016.
3). Son - Will be 19+ at the Time of Extension Application in May 2016.
My younger son is in College and studying as home student because he was under 18 years when he join college but my elder Son goes in University and doing Engineering (Undergraduate) as a Foreign Student (Higher Fees Payable then Home Student). Any how both Sons are Full Time Students and they never done any job/work for even 1 Hour nor they will do even we apply our Extension.
I have to Apply for Extension in May 2016, I request Some One can tell me the Rule of Extension after 3 years and then Indefinite visa after 5 years as my wife and Sons were my Dependents when I got Tier 1 (Entrepreneur) category visa in April 2013 because I think that we all should get the Extension after 3 years and then Indefinite visa after 5 years as we all get our Tier 1 (Entrepreneur) visa together.
May I know What is the Rule Applicable on me and my Family as we all are on Tier 1 (Entrepreneur) Visa.
Please write in Detail who knows the Rule as well who had Similar type of situation and when he apply what had happened with them (Case Study) as this will Help Many Readers who follow this Forum.
Thanks a Lot for the Help.