Sounds like you hit something a lot of people are hitting. No worries. I think you are working on a non public profile, so I can not watch along.
What you should do is replace the father of your sister with her correct father.
Go to edit on her profile. Then on the right you can see the father. Enter there via the edit/add link. On the top right you will see a small box. Paste the ID of her correct father in there. That is NAME-NUMBER, nothing more.
That should repair her link.
Then check if your father is not married to his mother. Make sure you have profiles for your father and his father.
If you want more help, then please add me to the trusted list of the profiles so I can watch along. I will remove myself once the links are working correctly.
edit - typo