Exceptional Talent - ILR for dependants

Dear Advisors,

I am currently in ICT(long tem visa, expires in Dec 2019).My ICT- dependants are my wife and 2 daughters. (younger one born in UK).

I am planning to apply for Tier-1 Exceptional Talent visa for myself and dependant visa for my family members.

The T1-(ET) Visa says, main Applicant can apply for ILR in 3 years and dependant can only apply after 5 years.

Now my question is,
Assuming, I am applying for 5 years visa for all of us.
In this case, after 3 years ,if I apply for ILR...

1. Will my family's T1(ET) dependant visa still valid?
2. In next 2 years (end of 5th year) , will they be eligible for applying ILR?


regards,
Joseph