Hey there
congrats on your twin preg!
I am with medibank private and YES you will have to swap over to family cover to ensure that the 2nd twin is covered. The second twin is not covered under singles cover!!!
Definately worth doing- my two were in hossy, NICU/special care for 33 days and the total bill that medibank covered- including 2 NETS ambo rides for one of my twins was over $120,000.00!!! and that was 6 years ago!!!

Dont get left short- sign up for family cover- even if it is until your twins are born and you are home!!
HTH
good luck
Odette