How much family income benefit do I need?

It depends on how much income your family may need to live from month to month. You can have this insurance as well as life insurance. You should have enough life insurance to repay all your mortgage and debts like credit cards and loans. You should now work out how much your family spends on bills like food, utilities council tax etc and insure for that amount per month. You can of course insure a higher amount, so your family have extra per month if you wish.