Eligibility check for F2 drop box

My query is: My family of 3 (wife, daughter & son) are having USA B1/B2 visa issued from USA Embassy in Kuwait, now i wanted to apply for F2 dependents from India (Hyderabad), are they eligible for Dropbox at USA consulate Hyderabad, India?

we left Kuwait, and we can not return. they are holding Indian passport.

They may be eligible as they already have a US visa issued in past.