What is the ruling on preventing the children of a sick person from visiting their father when the father is not harmed by the visit?

It is permissible for children to prevent visits to their father if such visits cause him harm, whether based on a doctor's request or the father's own wish. The children are more aware of what benefits or harms their father. However, if there is no reason for preventing visits, they should not do so. It might even be forbidden for them if the prevention extends to relatives, as this constitutes cutting off ties of kinship. Visiting the sick is a collective obligation (fard kifayah), and it can become an individual obligation (fard ayn) if the sick person is a relative and visiting them is considered a necessary part of maintaining kinship ties.