Suppose that a person is trying to submit an online-only version of USCIS I-134 (Affidavit of Financial Support) for a relative of that person and her child. It seems that the nline version of the form does not allow a person to list people travelling with the beneficiary. It seems that it is not in the "one form for the whole family" format, at least in it's online version. Some people suggest submitting a form for each person. On the other hand, it is not possible to submit this form for a young child, since such a child does not have a passport and this form cannot be completed until one supplies a valid passport number. The USCIS call center is not not able to answer the question.
What is the person expected to do in this scenario per the regulation? How did creators of this form intend the applicants to establish a relationship between the child and her mother?