If your family is filing multiple I-485 applications, it may be necessary to combine them. However, it’s very important to organize them separately.
If Form I-485 for a child age 13 or younger is filed in the same package with the Form I-485 of at least one parent, the fee for the child’s Form I-485 is reduced to $750. This is one example of why you may want to combine applications. But without some organization, you run the risk of mixing up applications and confusing USCIS. This could result in a unnecessary Request for Evidence or even a rejection.
Consider organizing each application in a separate envelope. For example, use a separate 9” x 12” envelope that includes one I-485, a separate check for USCIS fees, and supporting documents for each application. If you have a family of four, you’ll have four separate envelopes. Combine each of the envelopes into a separate package (or box). In this way, each application packet is organized separately but combined for the purposes of applying together.