Final answer:
Full-time grandparent care is especially likely when parents cannot care for their children due to drug abuse, incarceration, abandonment, or abuse, leading to grandparents or other relatives stepping in to provide primary care.
Step-by-step explanation:
Full-time grandparent care is especially likely when parents are unable to fulfill their caregiving roles due to various challenging circumstances. These include parental drug abuse, incarceration, mental health issues, or abandonment, which can leave the parent incapable of caring for their child. Moreover, extended family structures sometimes necessitate that grandparents step in as primary caregivers when other issues, such as physical or sexual abuse of the children by the parent, are present. About 54% of children who live with a guardian that is neither their biological nor adoptive parent reside with grandparents, indicating the prominent role grandparents play in such scenarios.