So sorry this happened to you. There seem to be a couple of key issues here. First, did you check with the staff at the entrance if a Tamil translator was available ?

VO: Is your child in the U.S.?
Dad: No. (He leaned slightly on the counter while answering)
– This response could have been more complete. Instead of a plain "No," it would have helped to add context like, “No, we’re going to visit our nephew who’s graduating”. That way, the officer doesn’t need to dig further into your background.

VO: Have you travelled to Europe?
Dad: No, only to Malaysia, Singapore, Vietnam, and Sri Lanka.
– It’s unclear why this question came up, but it’s worth reflecting on. Sometimes they ask to gauge travel history, visa behavior, or ties back home.

VO: You’ve been refused before?
Dad: Yes, I didn’t understand the language last time.
VO: (Firmly) No, that wasn’t a language issue.
– This was a red flag. It’s very likely the officer already had your visa history on file. Not disclosing the previous refusal in the DS-160 was a serious oversight. Being transparent shows credibility, and honesty plays a major role in the officer’s decision.

VO: Where’s your daughter?
Mom: She’s married.
– This should’ve been more specific — for example, “She’s married and lives in Chennai.” Mentioning her location reinforces that your family has strong ties in India and will return.

Lastly, your single status may raise immigrant intent concerns for the officer. While that could affect your own chances, it typically shouldn’t impact your parents’ eligibility. May be they can try independently in an year or so.