For applicants looking to file a family adjustment of status as parents of a U.S. Citizen (IR-5), checklist to complete before mailing form I-485.
Note that if there are two parents, then there is going to be two I-485s (one for each parent), just like there is one I-130 for each parent.
Also note that there cannot be anyone other than the parent either on the I-130 or the I-485. In other words, parents of U.S. Citizens cannot add children to their Green Cards (no derivative applicants are allowed). Children of the sponsored parents will have either to be sponsored as 'sibling' under F4 by the parent's sponsor (if they share a common parent), and/or by the one of the parent under F2A or F2B after that parent obtained their Green Card.