"Hainele bunicilor sunt bătrâne."
Translation:The grandparent's clothes are old.
No one would say hainele sunt bătrâne. Instead vechi is more appropriate. The former is more about being old as a person.
Is grandparent plural or singular here? Plural possessive would be grandparents'. If it is NOT meant to be plural, then perhaps "grandfather's" should be accepted as an alternate answer.