Upvote:6
Following the links for visa application from the website of any U.S. consulate in India takes you to USTravelDocs.com, which appears to be the contractor handling the processing. I would thus take this site to be authoritative, and yes, your parents can appoint someone else to pick up their passports for them.
The Passport/Visa Collection Locations and Timings page provides a table of the documents required to pick up a passport; of interest to you is the second column under “Pick-up Information”:
Representative collecting passport — even in case of family members:
- A photocopy of applicant's government-issued photo ID
- Representative's original government-issued photo ID and 1 photocopy;
- Original authorization letter
In other words, if they were to ask a friend to pick up their passports for them, the friend would need to carry
Additionally, it looks like the passports need not be collected at the consulate or embassy itself. Under “Locations and Timings” there a link showing 28 additional locations which Stanley and Blue Dart will deliver to, although it seems you must have specified the delivery location in the original application.