Cannot start Family Sharing due to conflicting Apple IDs

I’m trying to do family sharing so I can share my Apple Music subscription with my family. When I go to settings and tap family it says “cannot start family sharing” because my appleID is already used in my husband’s family but he doesn’t have that appleID. His phone is through his employer. I don’t know how to fix this.

[Re-Titled by Moderator]

Original Title: Family Sharing