Tier 2 General Visa renewal for dependents

Hello! I came to this country thru a tier 2 general visa last 2015. My visa will expire on 2018. I have 2 children which i want to apply a visa for this year to join me here in the UK. My questions are:
1) once my visa will expire and up for renewal, will it be the same for my dependents as well or will the expiration of their visa depend on when they applied?

2) if yes, will the fees i will be paying for the same as when i applied for their visa the first time around?

Thanks.

1) once my visa will expire and up for renewal, will it be the same for my dependents as well or will the expiration of their visa depend on when they applied?

Their visa will be issued with the same expiry as yours, not any longer than that. You will have to apply for an extension for them at the same time as yours.

2) if yes, will the fees i will be paying for the same as when i applied for their visa the first time around?

You will pay the fees applicable at the time of application. Fees have just gone up on 6th April and go up around the same time every year. You will all also have to pay the immigration health surcharge again for each person (yourself included).

Where is the other parent??