a little bit more info is required. Based on what you've written the best anyone can do is MAYBE...
Does the non-custodial parent have frequent access to the child? how frequent?
Did the child live with Grandma before primary carer died?
Are there any court orders pertaining to the child?
Are there any court orders pertaining to the no primary carer? For example does the non primary carer have an avo against them that protects the child?
Does the non-custodial parent have a history of drug abuse / child abuse / criminal behaviour?