Consent to transfer of custody question

Does anyone know of a basic form I can obtain(online) for my mother-in-law to obtain custody of her grandchild, which the aunt had custody and has agreed to sign such. She lives on disability income and funds are meager. The father, my brother-in-law, lost custody six years ago when he went to prison. So, the parents are not an issue unless child support is requested from the grandmother. Thank you for any advice.