PCOS is genetic. It’s capable of skipping generations though so that might be where the confusion is coming from. If you know a lot about the women in your family history, you can probably look back and find one or two of them with fertility issues or with the other symptoms of PCOS. These symptoms could have been explained away by other things that they actually knew about at the time. There are several women on my mom side a few generations back that retrospectively probably had it. They just didn’t know what it was at the time they were alive. Try to learn about family history if you can. You’ll probably find something.