If the principal investor’s derivatives (such as a child or spouse) were not included with the Form I-829, Petition by Investor to Remove Conditions on Permanent Resident Status, and intend to file their own Form I-829, can they file together on a single Form I-829?

They can only file together if the investor is deceased. Otherwise, each derivative must file a separate Form I-829 petition. If the derivative is filing a separate petition from the investor, the derivative should attach a copy of the investor’s Form I-797, Notice of Action, relating to the investor’s Form I-829.