The correct answer is remote grandparents.
Remote grandparents refer to grandparents who only occasionally spend time with or interact with their grandchildren due to physical and/ or emotional separation. Grandparents might be physically and/ or emotionally separated from their grandchildren due to reasons such as living far away from each other or due to a divorce of the children's parents. Since Luisa and Mark only see and spend time with their grandchildren during holidays, they can be considered remote grandparents.