My married sims now are half siblings?

Hello! I have the new Royalty and Legacies pack and my sim married Cordelia Thebe V. The two had four children but suddenly on the family tree it no longer says they are married but half sisters. The romance option is still available when interacting but the only option is offer massage. So it currently looks like two sisters decided to have children together. I have tried cheating it, I have tried Mc command center and I have tried going back to previous saves but it always changed from spouses to half siblings and I am losing my mind.