Questions involving parental versus grandparent custody

FIRST OF ALL, I’M VERY SORRY THAT THIS IS SO LONG…I JUST WANT TO STATE ALL OF THE FACTS FIRST

I do not know of any specific cases off hand that would apply here, and case law research is beyond the scope of this forum. I can say however that in my opinion the father would have to show there has been a substantial change in circumstances affecting the child’s best interest prior to attempting to modify the current schedule.