The Eleventh Circuit has determined an applicant is not eligible for non-LPR cancellation of removal when his child turned 21 after filing the application but before the merits hearing. The court declined to determine if an exception to this rule would apply when there was undue delay by the court in hearing the application, finding no such delay in this case.
The full text of Diaz-Arellano v. US Attorney General can be found here:
https://media.ca11.uscourts.gov/opinions/pub/files/202212446.pdf