Have any public institution employees ever taken family care leave?

‌Both of my parents are ill, so I am planning to take one year of family care leave.
I looked up the regulations, but they are quite vague.
It basically just says that leave can be granted if long-term recuperation is required.
My mother is currently recuperating after cancer surgery, and she is just staying at home.
However, she has difficulty walking and is naturally frail, so she cannot be left alone. My older brother visits her every day while working to cook meals and clean the house.
What I am curious about is whether a strict medical certificate is required for a one-year care leave.
Is it not enough to simply state that she underwent cancer surgery?
Is a medical certificate stating something like "requires long-term recuperation for more than one year" mandatory?
I am wondering if they demand very rigorous documentation.
She is in her late 70s, had cancer surgery a year ago, and because she is naturally frail, she has hardly been able to travel anywhere.
If there are any public institution employees who have taken family care leave, I would love to hear your advice.
ps) It is unpaid, but since I am not in a difficult financial situation, it is not hard for me to give up an annual salary of over 100 million KRW.