在哪个州？Google

Google "can subcontractor sue homeowner in XX state". 

XYZ as a subcontractor, they have no contractual relationship with your parents (homeowner).  They cannot sue the homeowner unless the homeowner somehow made certain statement/gurrantee to form an "implied contract".  I doubt your parent is even aware of XYZ.

This lien can be removed, whatever you think it will become "active" is probably incorrect.  Let me know your state and I can provide some links to local laws.