11/16/2011 at 05:00 PM EST
It's been nearly two years since Susan Powell disappeared
, but her father says her two young sons are coping well.
In September, Susan's parents, Charles and Judy Cox, gained custody
of Charlie Powell, 6, and Braden Powell, 4. The decision came after the discovery that their father Josh Powell was under investigation
for child pornography and continues to be a person of interest in the ongoing investigation
into Susan's December 2009 disappearance.
According to court documents, Charles Cox noted that the boys were seeing both a counselor and a therapist who was working with them "on a number of issues," the Deseret News reports
While Cox said in his court filing that his grandsons have been going to birthday parties, carving pumpkins, catching bugs and looking for frogs since moving into his home, it appears one of the boys is "somewhat reluctant" to work with the therapist.
Although the boy is doing well in school, Cox said he was "having nightmares" and was "afraid of the dark."
While the court allows Josh to see his sons for three hours on Sundays, Cox attests that the boys return from those visits "obstinate and more openly defiant than normal."
Cox also filed a motion requesting a copy of Josh's psychological evaluation, which he was ordered to undergo by the court.