What happens when a grand parent files for guardianship of a child?

our daughter has primary custody of our grand baby. she got herself strung out on drugs and of course, could no longer parent. the biological dad has been gone, by choice for 3 years, no child support. the cyfd placed the baby with us. we had a family meeting on thursday and the MIA dad and his whole family showed up at this meeting. like i said, he owes over 20k in child support and just chose to stay away... he too use to have a drug problem. they went to the meeting in hopes that the cyfd would place the baby with them, but that didn't happen. we got an attorney and he was served the very next day. my daughter signed willingly, cause she's the primary custodian.she was served in rehab. what will the biological dad have to do now? we have helped raise this child and when it was evident that my daughter was drifting off into the abyss, she left her with us.the biological dad has never sent the baby a b-day card, christmas card, no gifts, no child support... my question is, does he have to respond, or can he just let it ride if he desires? thank you so much.