I think you are misinterpreting something.
Family sharing has no effect on downloading apps directly. When you download an app, if just downloads form the App Store without Family Sharing getting involved. If you were in family sharing and bought an app, it would simply download the app and charge the purchase to the Family Organizer, but would not say much to you about it unless the family organizer's payment method had an issue.
Nobody can unilaterally add your Apple Account to Family Sharing. And even if they did, all that would do is make it so purchases would be charged to the organizer instead of you directly.
What exactly is happening?
How exactly is Family Sharing coming up exactly?
Do you get an error message? If so, what does it say?
If you explain exactly what is happening, we may be able to offer a course of action.