Hello dear PCOS is a hormonal
disease which affects menstruation
and conception. Obesity, acne
, excessive hair are all part of this disease. It has some element of genetic involvement but many other factors are also involved. Moreover if you have regular periods and adequate flow then nothing to worry as of today. And your sister should get her surgery done to deal with the cyst, PCOS and also it will tell the status of her fallopian tubes so as to look for the cause of infertility
if any. Wish you and your sister a very good health. Take care.