Thanks Susie,
i actually used all information relevant to each applicant throughout the applications. However, by the end of each application, I noticed from samples that you need to enter passport number to complete “sign and submit” screen, so not sure if that passport number refers to applicant (minor child) or the signer (parent/principal applicant)
I am completing DS260 for a friend and his family, so the process was quiet different from what I expected. I hope those who completed DS 260 for multiple family members under one case number can help!🙏