If a derivative was listed on the I-526 Petition but simply failed to adjust status or consular process at the time of I-526 approval, it may be possible to apply for the adjustment of status through Form I-485 after approval of the I-829 Petition. Alternatively, the derivative may have to file for following-to-join benefits, or the principal applicant might have to file Form I-130, Petition for Alien Relative. The specific course of action will depend on the circumstances of the case, and so it is important to retain experienced immigration counsel.